Definition of


  1. (noun, quantity) a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
  2. (noun, quantity) (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
  3. (noun, communication) the 18th letter of the Roman alphabet
  4. (noun, attribute) the length of a line segment between the center and circumference of a circle or sphere

via WordNet, Princeton University

Origin of the word R

  1. In a circle, meaning "registered (trademark)," first incorporated in U.S. statues 1946. Three Rs (1825) said to have been given as a toast by Sir W. Curtis (1752-1829). R&R "rest and relaxation," first recorded 1953, Amer.Eng.; R&B "rhythm and blues" (type of popular music) first attested 1949, Amer.Eng. more

via Online Etymology Dictionary, ©2001 Douglas Harper

Words that sound like R

r-2, ra, rahu, raiu, rare, rariora, raw, ray, re, rear, rehear, rewa-rewa, rewire, rh, rhea, rho, ri, rio, rira, ro, roar, roarer, roe, roi, roue, row, rower, ru, ru 486, rue

via soundex() Hash Matches

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Baron Karl Maria Friedrich Ernst Von Weber

German conductor and composer of romantic operas (1786-1826)