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definitions

smartmouth

noun informal
  1. a witty or sarcastic person
  2. witty or sarcastic comments
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for smartmouth
n.

1968, from smart (adj.) + mouth (n.).

Online Etymology Dictionary, © 2010 Douglas Harper