crack
adjective/kræk/
/kræk/
[only before noun]- expert and highly trained; excellent at something
- crack troops
- He's a crack shot (= accurate and skilled at shooting).
Word OriginOld English cracian ‘make an explosive noise’; of Germanic origin; related to Dutch kraken and German krachen. Sense (8) of the noun is from Irish craic ‘entertaining conversation’.
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crack