18-letter words containing a, r, i, d
- potential gradient — the rate of change of potential with respect to distance in the direction of greatest change.
- predation pressure — the effect of predation upon a population, resulting in the decrease in size of that population.
- predicate calculus — predicate logic
- presenile dementia — a form of dementia, of unknown cause, starting before a person is old
- preservation order — In Britain, a preservation order is an official order that makes it illegal for anyone to alter or destroy something such as an old building or an area of countryside.
- presidential suite — a suite of rooms, as in a hotel, suitable for a president or other head of state.
- prestidigitization — /pres`t*-di"j*-ti:-zay"sh*n/ 1. A term coined by Daniel Klein <[email protected]> for the act of putting something into digital notation via sleight of hand. 2. Data entry through legerdemain.
- price on sb's head — If there is a price on someone 's head, an amount of money has been offered for the capture or killing of that person.
- primate of england — a title of the archbishop of Canterbury.
- prince of darkness — Satan.
- principal diagonal — a diagonal line or plane.
- principal meridian — a meridian line accurately laid out to serve as the reference meridian in land survey
- prisoner's dilemma — (in game theory) a scenario in which the outcome of one person's decision is determined by the simultaneous decisions of the other participants, resulting in a bad outcome for all of them if all act in their own self-interest.
- production company — an organization which produces, films, plays, television or radio programmes
- production manager — a supervisor of the budget, crew and other details in the production of a film or play
- propaganda machine — the group of people, publications, etc, such as of a government, country etc, responsible for the organized dissemination of information, allegations, etc, to assist or damage the cause of a government, movement, etc
- protocol data unit — (PDU) A packet of data passed across a network. The term implies a specific layer of the OSI seven layer model and a specific protocol.
- provably difficult — The set or property of problems for which it can be proven that no polynomial-time algorithm exists, only exponential-time algorithms.
- pseudo-anarchistic — a person who advocates or believes in anarchy or anarchism.
- pyramus and thisbe — (in Greek legend) two lovers of Babylon: Pyramus, wrongly supposing Thisbe to be dead, killed himself and she, encountering him in his death throes, did the same
- pyromucic aldehyde — furfural.
- pyrosulphuric acid — a fuming liquid acid made by adding sulphur trioxide to concentrated sulphuric acid. Formula: H2S2O7
- qattara depression — a desert basin in the Libyan Desert, in NW Egypt: lowest point is 435 feet (133 meters) below sea level. 6950 sq. mi. (18,000 sq. km).
- quadratic equation — an equation containing a single variable of degree 2. Its general form is ax 2 + bx + c = 0, where x is the variable and a, b, and c are constants (a ≠ 0).
- quarry-tiled floor — a floor covered with square or diamond-shaped unglazed floor tiles
- quartz-iodine lamp — a type of tungsten-halogen lamp containing small amounts of iodine and having a quartz envelope, operating at high temperature and producing an intense light for use in car headlamps, etc
- quinacrine mustard — a nitrogen mustard derived from mepacrine and used as a stain for chromosomes
- racially motivated — motivated by (the hate or prejudice of) someone's race
- radiant efficiency — the ratio of the power emitted by a source of radiation to the power consumed by it
- radiation exposure — exposure to radiant energy or to the particles emitted in the transfer of radiant energy, esp the particles and gamma rays emitted in nuclear decay; exposure to radioactive substances
- radiation pressure — the pressure exerted on a surface by electromagnetic radiation or by sound waves.
- radiation sickness — sickness caused by irradiation with x-rays or other nuclear radiation as a result of therapeutic treatment, accidental exposure, or a nuclear bomb explosion and characterized by nausea, vomiting, headache, cramps, diarrhea, loss of hair and teeth, destruction of white blood cells, and prolonged hemorrhage.
- radical empiricism — (in the philosophy of William James) the doctrine that the only proper subject matter of philosophy is that which can be defined in terms of experience, and that relations are a part of experience.
- radical expression — an expression in which radical signs appear.
- radio range beacon — a radio transmitter that utilizes two or more directional antennas and transmits signals differing with direction, permitting a flier receiving a signal to determine his or her approximate bearing from the transmitter without a radio compass.
- radioactive dating — any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product.
- radioactive series — a succession of elements initiated in the radioactive decay of a parent, as thorium or uranium, each of which decays into the next until a stable element, usually lead, is produced.
- radiocarbon dating — the determination of the age of objects of organic origin by measurement of the radioactivity of their carbon content.
- radiocommunication — communication by means of radio waves
- radiometric dating — any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product.
- radius of gyration — the distance from an axis at which the mass of a body may be assumed to be concentrated and at which the moment of inertia will be equal to the moment of inertia of the actual mass about the axis, equal to the square root of the quotient of the moment of inertia and the mass.
- ragtag and bobtail — the riffraff; rabble: The ragtag and bobtail of every nation poured into the frontier in search of gold.
- rail rapid transit — a system of rail transit within an urban area that has exclusive right of way either below, above, or on the ground and so is capable of relatively high operating speed. Abbreviation: RRT.
- rain cats and dogs — water that is condensed from the aqueous vapor in the atmosphere and falls to earth in drops more than 1/50 inch (0.5 mm) in diameter. Compare drizzle (def 6).
- rapid eye movement — rapidly shifting, continuous movements of the eyes beneath closed lids during the stage of sleep characterized by dreaming.
- rear its ugly head — the upper part of the body in humans, joined to the trunk by the neck, containing the brain, eyes, ears, nose, and mouth.
- reduction strategy — (theory) An algorithm for deciding which redex(es) to reduce next. Different strategies have different termination properties in the presence of recursive functions or values. See string reduction, normal order reduction, applicative order reduction, parallel reduction
- refrigerated lorry — a lorry which is chilled in the back as for storing food
- reggio di calabria — a seaport in S Italy, on the Strait of Messina: almost totally destroyed by an earthquake 1908.
- registered charity — official aid organization