mm.

1. Music. measures.

2. thousands. [ < L millia]

3. millimeter; millimeters.

* * *

mm. or mm (no period),

1. millimeter or millimeters.

2. thousands (Latin, millia).

mm.² or mm² (no period),

square millimeter.

mm.³ or mm³ (no period),

cubic millimeter.

MM.,

1. (Their) Majesties.

2. Messieurs.

Usage See Messrs. for usage note.

M.M.,

Master of Music.