tap on

tap on something

to make one or more light blows on something. Who is that tapping on my windowpane? I wish you would stop tapping on the tabletop.
See also: on, tap

tap someone or something on something

to make one or more light blows on some part of someone or something. Someone tapped me on the shoulder, and I turned around to see who it was. I tapped the drum on the top to find its pitch.
See also: on, tap
References in classic literature ?
Rouletabille, with a friendly tap on my shoulder, confessed that he had nothing more to learn at the Glandier; he had learned there all it had to tell him.
My aunt Starkweather settled the question by a second tap on my shoulder.
Leo Hunter, bestowing another tap on the slumbering lion of the Eatanswill GAZETTE.
Felix and Dan were already sound asleep; I was drifting near the coast o' dreams when I was aroused by a light tap on the door.