tap (n.)

A term used in the PHONETIC classification of CONSONANT sounds on the basis of their MANNER OF ARTICULATION: it refers to any sound produced by a single rapid contact with the roof of the mouth by the TONGUE, resembling a very brief articulation of a STOP. It is commonly heard in many American English pronunciations of the medial /t/ or /d/ in writer and rider. Some phoneticians distinguish between taps and FLAPS in terms of the articulatory movements involved.