What is "sprained"

Sprain \Sprain\ (spr[=a]n), v. t. [imp. & p. p. Sprained (spr[=a]nd); p. pr. & vb. n. Spraining.] [OF. espreindreto press, to force out, F. ['e]preindre, fr. L. exprimere. See Express, v. t., and cf. Spraints.] To weaken, as a joint, ligament, or muscle, by sudden and excessive exertion, as by wrenching; to overstrain, or stretch injuriously, but without luxation; as, to sprain one's ankle.

vb. (en-past of: sprain)