Entry 2 senses · 2 variants Webster, 1913 Flex /flĕks/ · IPA /flɛks/ v. t. n. 01 v. t. To bend; as, to flex the arm. imp. & p. p. Flexed; p. pr. & vb. n. Flexing 1. To bend; as, to flex the arm. 02 n. Flax. 1. Flax.[Obs.]