strum / strəm/ • v. (strummed, strum·ming) [tr.] play (a guitar or similar instrument) by sweeping the thumb or a plectrum up or down the strings. ∎ play (a tune) in such a way: he strummed a few chords. ∎ [intr.] play casually or unskillfully on a stringed or keyboard instrument.• n. [in sing.] the sound made by strumming: the brittle strum of acoustic guitars. ∎ an instance or spell of strumming.DERIVATIVES: strum·mer n.