The labial flap is a speech sound which has received little attention in the literature. In this paper, we document the articulation of the sound, including audio and video data from Mono (D.R. Congo, Ubangian). The sound is attested in over sixty languages and has been incorporated into the phonological system of at least a dozen of them. The sound is easily describable in terms of values of phonological features or phonetic parameters, and it appears to have arisen independently in at least two regions of the world. These factors argue for the inclusion of the sound in the International Phonetic Alphabet.