motormouth

/M OW1 T ER0 M UW1 TH/
noun
  1. 1

    One who talks very fast or incessantly; a chatty or loquacious person.

    โ€œHe's such a motormouth that I can never get a word in.โ€

verb
  1. 1

    To talk very fast or incessantly.

Source: https://en.wiktionary.org/wiki/motormouth