Britishthermal unit

British thermal unit n. Abbr. BTU or Btu

1. 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.

2. 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.

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