The definition of a barb is a very strong insult or criticism.(noun)
Telling someone to drop dead is an example of a barb.
See barb in Webster's New World College Dictionary
Origin: ME & OFr barbe < L barba, beard
Origin: Fr barbe, Barbary horse < It barbero < Ar Barbar, Berber
See barb in American Heritage Dictionary 4
Origin: Middle English barbe
Origin: , from Old French, beard
Origin: , from Latin barba; see bhardh-ā- in Indo-European roots.
Origin: French barbe
Origin: , from Italian barbero, Berber
Origin: , from Vulgar Latin Barbaria, Barbary States
Origin: , from Latin barbarus, barbarous; see barbarous.
Learn more about barb