(often + with) to play absentmindedly with something; to fiddle with it
archaic to turn or twirl lightly
to rotate or twist (something) lightly or idly
He twiddled the knob on the radio
twiddle one's thumbs
to have nothing to do; to be bored or idle
twiddler noun
[prob imitative, perhaps a blend of twirl1 or twist1 + fiddle2]