Witty, clever retort

One word substitute is Repartee.

Sarcasm: the use of irony to mock or convey contempt.
Repartee: conversation or speech characterized by quick, witty comments or replies.
Platitude: a remark or statement, especially one with a moral content, that has been used too often to be interesting or thoughtful.
Invective: insulting, abusive, or highly critical language.