noun: A person who is characterized by "shady", strange, underhanded, devious or sly acts or behavior.
Adj: Describes a person who has acted shadily towards you or someone else.
"Hey, shae dibbly! Stop looking at internet porn on my parents' computer."
"Why do you always have to act so shae dibbly after you have a few drinks? You smashed a beer bottle on the bar and tried to cut me with the jagged edge last night."