contrary to the laws or course of nature.

at variance with the character or nature of a person, animal, or plant.

at variance with what is normal or to be expected

the unnatural atmosphere of the place.

lacking human qualities or sympathies; monstrous; inhuman

an obsessive and unnatural hatred.

not genuine or spontaneous; artificial or contrived

a stiff, unnatural manner.

Obsolete . lacking a valid or natural claim; illegitimate.

noun

aberrance , aberrancy , aberration , anomaly , deviance , deviancy , deviation , irregularity , preternaturalness