Formal:
* Retort: A sharp, witty, or angry reply.
* Repartee: A quick, clever, and often humorous exchange of replies.
* Counterargument: A reasoned reply that challenges the original statement.
* Rebuttal: A formal reply that refutes or disproves an argument.
Informal:
* Snap back: A quick, angry, or sarcastic reply.
* Mouth off: To speak rudely or defiantly.
* Talk back: To reply rudely or disrespectfully.
* Give it back to someone: To retaliate with a sharp or witty reply.
More specific:
* Insolent: Rude and disrespectful.
* Impertinent: Rudely disrespectful.
* Flippant: Lacking seriousness or respect.
* Contumacious: Stubbornly disobedient.
* Incendiary: Likely to provoke anger or violence.
The best word to use will depend on the context and the specific tone you want to convey.