It is an adjective.
Meaning: Being different from normal; deviating from the usual way of doing things.
It is used in a negetive sense i.e if you refer it to a person then it signifies that you do not like the difference exhibited by him/her.
Synonyms : abnormal, odd, strange, bizarre, eccentric
aberrance, aberrancy - noun
aberrantly - adverb
1) Terrorists are aberrant creatures.
2) You should be different from the society in doing good things, but I do not enchorage having aberrancy.