British thermal unit
n. Abbr. BTU or Btu
► The quantity of heat required to raise the temperature of one pound of water from 60° to 61°F at a constant pressure of one atmosphere.
► The quantity of heat equal to ¹/₁₈₀ of the heat required to raise the temperature of one pound of water from 32° to 212°F at a constant pressure of one atmosphere.

[TahlilGaran] American Dictionary ▲