1)part of foreplay that definitely requires an art other than 'sticking your fingers in a pussy' as delineated in previous definitions. many males still don't understand this, but true fingering will also constitute stimulation of the clitoris using fingers. if you are truly talented, you can do both at the same time. we appreciate that ;)
2) it can also refer to the insertion of fingers into the anus, or indeed any cavity, for sexual pleasure and stimulation.
1) "hey, you know that guy I was with on saturday? he was fingering me at the bar!"
2) dude you would not believe this but my mom walked in on me fingering my own ass last night...