Deviance refers to a state that is veering away from the norm. Wearing a chicken suit to work would definitely be an example of deviance, unless of course you're a mascot.
If you know that deviating means to depart from what's normal, you won't be surprised that deviance is a condition of abnormal or aberrant behavior. Deviance includes behavior that is considered weird, odd, and strange. Sometimes, deviance could include illegal behavior. Since people don't agree on what's normal, they don't agree on what counts as deviance either.