・a crack hand 妙手, 名人.

・a crack performer 名演技[演奏]者.

・a crack regiment 精鋭連隊.

・a crack shot 名射手.

adv. ぱちっと, ぴし(ゃ)りと, 鋭く (sharply).

・hit a person crack in the eye 人の目をぴしゃっと打つ.

・The pistol went off crack. ピストルがぱーんと鳴った.

ME crak(k)e(n) to creak ＜ OE cracian to crack, resound ← Gmc kre- ← IE ger- to cry hoarsely: cf. creak, croak, crow^１，２ crack・a・jack /krkdk/

n., adj. 《口語》 ＝crackerjack. crck bby