The terms tap and flap may be used interchangeably.
Peter Ladefoged proposed for a while that it may be useful to distinguish between them. However, his usage has been inconsistent, contradicting itself even between different editions of the same text. The last proposed distinction was that a tap strikes its point of contact directly, as a very brief plosive, whereas a flap strikes the point of contact tangentially: "Flaps are most typically made by retracting the tongue tip behind the alveolar ridge and moving it forward so that it strikes the ridge in passing." However, later on, he no longer felt this was a useful distinction to make, and preferred to use the word flap in all cases.
For linguists who do make the distinction, the coronal tap is transcribed as a fish-hook "r", [ɾ], while the flap is transcribed as a small capital "d", [ᴅ], which is not recognized by the IPA. Otherwise, alveolars and dentals are typically called taps, and other articulations flaps. No language contrasts a tap and a flap at the same place of articulation.
This sound is often analyzed (and therefore transcribed) by native English speakers as an 'R-sound' in many foreign languages. For example, the 'Japanese R' in hara, akira, tora, etc. is actually an alveolar tap. In languages where this segment is present but is not a true phoneme, an alveolar tap is often an allophone of either an alveolar stop (/t/ or /d/) or an 'R-sound' i.e. an alveolar trill or alveolar approximant.
Carbonell, Joan F. & Joaquim Llisterri (1992), "Catalan", Journal of the International Phonetic Association22 (1-2): 53-56
Cox, Felicity & Sallyanne Palethorpe (2007), "Australian English", Journal of the International Phonetic Association37 (3): 341-349
Cruz-Ferreira, Madalena (1995), "European Portuguese", Journal of the International Phonetic Association25 (2): 90-94
Martínez-Celdrán, Eugenio; Ana Ma. Fernández-Planas & Josefina Carrera-Sabaté (2003), "Castilian Spanish", Journal of the International Phonetic Association33 (2): 255-259
Watson, Janet (2002), written at New York, The Phonology and Morphology of Arabic, Oxford University Press
Watson, Kevin (2007), "Liverpool English", Journal of the International Phonetic Association37 (3): 351-360
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Where symbols appear in pairs, the one to the right represents a voiced consonant. Shaded areas denote pulmonic articulations judged impossible.