■ noun a unit of heat, especially as the former statutory unit of gas supplied in the UK equivalent to 100,000 British ~al units or 1.055 × 10 8 joules.
Origin
1920s: from Gk ~ē 'heat'.
THERM
Meaning of THERM in English
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004