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Webster 1828 Edition

ppr.

Striking; beating; moving something broad; as flapping wings. The ducks run flapping and fluttering.

flapping ‎(not comparable)

flapping ‎(countable and uncountable, plural flappings)

An instance where one flaps.
(phonology) A phonological process found in many dialects of English, especially American English and Canadian English, by which intervocalic /t/ and /d/ surface as the alveolar flap /ɾ/ before an unstressed syllable, so that words such as "metal" and "medal" are pronounced similarly or identically.
(computing, telecommunications) The situation where a resource, a network destination, etc., is advertised as being available and then unavailable (or available by different routes) in rapid succession.

flapping