the highest ranking non-commissioned officer in a company or equivalent unit.

A non-commissioned officer of the highest grade.

the highest-ranking non-commissioned officer of an infantry company.

sergeant-major.

elliptical for top sergeant n. at compounds 3a below. U.S. Military slang.

first sergeant.

British Services' slang. A (usually regimental) sergeant-major; (also) a senior Royal Marine officer.

Regimental Sergeant Major.

= top sergeant n. below.

= top sergeant n. below.

= sergeant-major, n. 2 (Frequently used as a form of address.)

= top sergeant n. above.

= sergeant-major, n. 2. Cf. Sar-Major, n.