Simple past tense and past participle of strum.(verb)
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Use "strummed" in a sentence
"His self-accompaniment consists of a repetitive one-chord (maybe two) guitar strum that predates Jandek and a toy piano that is "strummed" and sounds like a lysergic zither from the Third Man soundtrack."
"A special shout-out to Holly Fisher, who wrote this song for me, he said, and strummed the first chords."
"Holly strummed a few more chords, finding the right key."