Definition of "gab"

gab¹

/ɡæb/

noun
countable and uncountable, plural gabs
1. Idle chatter.
2. The mouth or gob.
3. One of the open-forked ends of rods controlling reversing in early steam engines.
  Quotations
  Loose eccentric reversing gear gave way about 1836 to the early forms of gab motion. [...] In 1840 Stephenson evolved a motion in which the gabs were connected directly to the valve spindle.
  1940 July, S. Richards, “Locomotive Valve gear Development”, in Railway Magazine, page 412

gab²

/ɡæb/

verb
third-person singular simple present gabs, present participle gabbing, simple past and past participle gabbed
1. (intransitive, obsolete) To jest; to tell lies in jest; exaggerate; lie.
  Quotations
  He would chant his own doughty deeds, and “gab,” as the Norman word was, in painful earnest, while they gabbed only in sport, and outvied each other in impossible fanfaronades”
  1866, Charles Kingsley, chapter 12, in Hereward the Wake, London: Nelson, page 181
2. (intransitive) To talk or chatter a lot, usually on trivial subjects.
  Quotations
  "That Mrs. Mender gives a bloke the ear-ache; thinks a bloke's got all day to waste listening to her gab."
  1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, page 26
3. (transitive, obsolete) To speak or tell falsely.