- (botany, zoology) Deviating from the ordinary or natural type; exceptional; abnormal. [First attested in the mid 19th century.]
- (sometimes figuratively) Straying from the right way; deviating from morality or truth. [First attested in the mid 18th century.]
- Differing from the norm. [Attesting from the mid 16th century until the early 17th century.]
- A person or object that deviates from the rest of a group.
- (biology) A group, individual, or structure that deviates from the usual or natural type, especially with an atypical chromosome number.