28-letter words containing c, l, a, s, d, r
- united states postal service — an independent federal agency created in 1971 to replace the Post Office Department as the division of the federal government responsible for postal services. Abbreviation: USPS.
- zeroth law of thermodynamics — the principle that any two systems in thermal equilibrium with a third system are in thermal equilibrium with each other. Compare law of thermodynamics (def 2).