21-letter words containing a, c, r, o
- recompression chamber — hyperbaric chamber.
- reconnaissance flight — a flight made by an aircraft in order to obtain military information about a particular place
- reconnaissance patrol — a patrol made by soldiers in order to obtain military information about a particular place
- record of achievement — a statement of the personal and educational development of each pupil
- rectangular hyperbola — a hyperbola with perpendicular asymptotes
- red-headed woodpecker — a black and white North American woodpecker, Melanerpes erythrocephalus, having a red head and neck.
- redevelopment company — a private corporation or a public agency that stimulates the improvement of land, as through a building project subject to certain designs and controls, by financing, selling, or leasing such real estate to interested buyers or lessees.
- registration document — a document giving identification details of a motor vehicle, including its manufacturer, date of registration, engine and chassis numbers, and owner's name
- rehabilitation centre — a centre or clinic where people with an alcohol or drug addiction are treated
- reinforcement therapy — a behavior modification technique in which appropriate behavior is strengthened through systematic reinforcement.
- relaxation oscillator — a nonsinusoidal oscillator, the timing of which is controlled by the charge and discharge time constants of resistance and capacitance components
- remote procedure call — (networking, programming) (RPC) A protocol which allows a program running on one host to cause code to be executed on another host without the programmer needing to explicitly code for this. RPC is an easy and popular paradigm for implementing the client-server model of distributed computing. An RPC is initiated by the caller (client) sending request message to a remote system (the server) to execute a certain procedure using arguments supplied. A result message is returned to the caller. There are many variations and subtleties in various implementations, resulting in a variety of different (incompatible) RPC protocols.
- replacement algorithm — The method used to determine which entry in an associative cache to flush to main memory when it is desired to cache a new block of data. The "least recently used" algorithm flushed the block which has not been accessed for the longest time. A random replacement algorithm picks any block with equal probability.
- retarded acceleration — velocity increase constrained by opposing forces such as wind resistance or braking
- reverberation chamber — a room with walls that reflect sound. It is used to make acoustic measurements and as a source of reverberant sound to be mixed with direct sound for recording or broadcasting
- reverberatory furnace — See at reverberatory (def 2).
- richard coeur de lion — ("Richard the Lion-Hearted"; "Richard Coeur de Lion") 1157–99, king of England 1189–99.
- ring down the curtain — to lower the curtain at the end of a theatrical performance
- road traffic accident — an accident involving vehicles
- rocky mountain locust — a migratory locust, Melanoplus spretus, that occurs in North America, especially the Great Plains, where swarms cause great damage to crops and other vegetation.
- rocky mountain oyster — mountain oyster.
- roman catholic church — the Christian church of which the pope, or bishop of Rome, is the supreme head.
- royal victorian order — (in Britain) an order of chivalry founded by Queen Victoria in 1896, membership of which is conferred for special services to the sovereign
- rutherford scattering — the scattering of an alpha particle through a large angle with respect to the original direction of motion of the particle, caused by an atom (Rutherford atom) with most of the mass and all of the positive electric charge concentrated at a center or nucleus.
- s-k reduction machine — An abstract machine defined by Professor David Turner to evaluate combinator expressions represented as binary graphs. Named after the two basic combinators, S and K.
- saint anthony's cross — tau cross.
- sao bernardo do campo — a city in SE Brazil, SE of São Paulo.
- sao tome and principe — Democratic Republic of, a republic in W Africa, comprising the islands of São Tomé and Príncipe, in the Gulf of Guinea, N of the equator: a former overseas province of Portugal; gained independence in 1975. 372 sq. mi. (964 sq. km). Capital: São Tomé.
- saponification number — the number of milligrams of potassium hydroxide required to saponify one gram of a given ester, especially a glyceride.
- satisficing behaviour — the form of behaviour demonstrated by firms who seek satisfactory profits and satisfactory growth rather than maximum profits
- saving your reverence — a form of apology for using an obscene or taboo expression
- scalar multiplication — an operation used in the definition of a vector space in which the product of a scalar and a vector is a vector, the operation is distributive over the addition of both scalars and vectors, and is associative with multiplication of scalars
- scalar triple product — the volume of the parallelepiped defined by three given vectors, u, v, and w, usually represented as u·v 1 (v×w), [ uvw ], or (uvw), where × denotes a cross product and · denotes an inner product.
- scarlet monkey flower — any of various plants belonging to the genus Mimulus, of the figwort family, as M. cardinalis (scarlet monkey flower) having spotted flowers that resemble a face.
- schlieren photography — a type of photography which records schlieren
- school of hard knocks — the experience gained from living, especially from disappointment and hard work, regarded as a means of education: The only school he ever attended was the school of hard knocks.
- scintillation counter — a device for detecting and measuring radioactivity, having a crystal scintillator, a photoelectric cell sensitive to the light from scintillations, and an amplifier.
- scorched earth policy — a military practice of devastating the property and agriculture of an area before abandoning it to an advancing enemy.
- scorched-earth policy — a military practice of devastating the property and agriculture of an area before abandoning it to an advancing enemy.
- secondary containment — Secondary containment is a system for dealing with hazardous spills.
- secure hash algorithm —
- self-characterization — portrayal; description: the actor's characterization of a politician.
- seventeen-year locust — a cicada, Magicicada septendecim, of the eastern U.S., having nymphs that live in the soil, usually emerging in great numbers after 17 years in the North or 13 years in the South.
- sheppard's correction — a method of correcting the bias in standard deviations and higher moments of distributions that arises from grouping values of the variable.
- short message service — (messaging) (SMS) A message service offered by the GSM digital mobile telephone system. Using SMS, a short alphanumeric message (160 alphanumeric characters) can be sent to a mobile phone to be displayed there, much like in an alphanumeric pager system. The message is buffered by the GSM network until the phone becomes active.
- silicon tetrachloride — a colorless, fuming liquid, SiCl 4 , used chiefly for making smoke screens and various derivatives of silicon.
- silicon tetrafluoride — a colorless, fuming gas, SiF 4 , used chiefly in the manufacture of fluosilicic acid.
- simple actor language — (language) (SAL) A minimal actor language, used for teaching in:
- sinusoidal projection — an equal-area projection in which parallels are straight lines spaced at regular intervals, the central meridian is a straight line one-half the length of the equator, and the other meridians are curves symmetrical to the central meridian.
- siren call/siren song — A siren call or siren song is the appeal that something has although it is harmful or dangerous.