What is the meaning of barb?

noun

• An aggressive remark directed at a person like a missile and intended to have a telling effect.
  • usage: "his parting shot was `drop dead'"; "she threw shafts of sarcasm"; "she takes a dig at me every chance she gets"
  • synonyms: shot, shaft, slam, dig, jibe, gibe
• The pointed part of barbed wire.
• A subsidiary point facing opposite from the main point that makes an arrowhead or spear hard to remove.
• One of the parallel filaments projecting from the main shaft of a feather.

verb

• Provide with barbs.
  • usage: "barbed wire"