Describes a person of short and slight physical build. Often used in contrast with 大兵 (たいへい, large build).
He is small in stature, but very strong.
The small-build athlete threw the larger opponent.
Compound of 小 (small) and 兵 (soldier, here extended to mean build or physique). The exact historical derivation is uncertain, but the word is conventionally associated with describing a person's small physical frame.