The term BTU PART OF is composed of five crossword solutions: UNIT (4 letters), THERMAL (7 letters), THERM (5 letters), CAL (3 letters), and MEAS (4 letters). The acronym BTU stands for British THERMAL UNIT, which is a UNIT of energy used to measure heat. UNIT is short for UNIT of measurement, THERMAL refers to THERMAL energy, THERM is an abbreviation of thermodynamics, CAL is short for calorie, and MEAS is short for measure. Therefore, the term BTU PART OF can be interpreted as a part of the British THERMAL UNIT, which is a UNIT of energy used to measure heat.