The term 'THE R IN RPM' is a crossword puzzle clue that can be solved with the answers REV (3 letters) and REVS (4 letters). The answer to this clue is an abbreviation for the word revolutions, which is used to measure the speed of rotation of an object. Revolutions per minute (RPM) is a unit of measurement used to measure the number of rotations an object makes in one minute. The abbreviation 'REV' or 'REVS' is used to represent revolutions in this context.