If you strum a stringed instrument such as a guitar, you play it by moving your fingers backwards and forwards across the strings. In the corner, one youth sat alone, softly strumming a guitar Vaska strummed away on his guitar. Strum is also a noun. A little while later, I heard the strum of my father's guitar as he began to sing. to play an instrument such as a guitar by moving your fingers up and down across its strings (From the sound)