Other forms: strumming; strummed; strums
To strum is to play a guitar or another stringed instrument by brushing the strings with your fingers. It's pretty easy to strum a ukulele, but it sounds better if you know some chords.
You might tell the guitar player in your band, "Strum a few chords of that song we wrote yesterday." You can also strum idly on your sister's banjo without playing actual chords, just by running your thumb down the strings. Strum is a noun, too, meaning "the sound or act of strumming." This word dates from the 18th century, and experts think it's imitative, sounding a bit like an actual strum.