Satire (; in Eng. often , n.
Etymology: [L. satira, satura, fr. satura (sc. lanx) a dish filled with various kinds of fruits, food composed of various ingredients, a mixture, a medley, fr. satur full of food, sated, fr. sat, satis, enough: cf. F. satire. See Sate, Sad, a., and cf. Saturate.]
1. A composition, generally poetical, holding up vice or folly to reprobation; a keen or severe exposure of what in public or private morals deserves rebuke; an invective poem; as, the Satires of Juvenal.
2. Keeness and severity of remark; caustic exposure to reprobation; trenchant wit; sarcasm.
Syn. -- Lampoon; sarcasm; irony; ridicule; pasquinade; burlesque; wit; humor.
Shades of meaning
Fernald has no entry of its own for satire; he lists it under banter.
Where he writes about it:
A satire is a formal composition; a sarcasm may be an impromptu sentence. — from banter
The satire shows up follies to keep people from them; the sarcasm hits them because they are foolish, without inquiring whether it will do good or harm; the satire is plainly uttered; the sarcasm is covert. — from banter