noun

• (countable) The high-pitched bark of a small dog, or similar.
• (uncountable, slang) Casual talk; chatter.
  "Had I taken his accusations seriously I might have recommended a change in my under-managership, but I never could translate our jammy products into gas or explosives or even poison. Still yap, at least as concerned Beldite's."
• (countable, slang, derogatory) The mouth, which produces speech.
  "Shut your yap!"
• (countable, Geordie) A badly behaved person, especially a child.

verb

• (intransitive) Of a small dog, to bark.
• (intransitive, slang) To talk, especially excessively; to chatter.
  "You’re always yapping, I wish you’d shut up."
• (transitive, slang) To rob or steal from (someone).
  "Ante up! Yap that fool!"