For`mi*ca"tion (?), n. [L. formicatio, fr. formicare to creep like an ant, to feel as if ants were crawling on one's self, fr. formica ant: cf. F. formication.] (Med.) A sensation resembling that made by the creeping of ants on the skin. Dunglison.

• A hallucinated sensation that insects or snakes are crawling over the skin; to feel as if "bugs" were crawling on one's self. The tactile hallucination or illusion that insects are crawling on the body or under the skin. A common side-effect of extensive use of cocaine or amphetamines, it can also be experienced with high fevers.