Much like bench racing (i.e. estimating how one's car will kick another's car's ass, based purely on horsepower and feel of said cars; often done while kickin' back a few brews with your bros), bench fucking includes, but is not limited to, drooling over/ogling a girl/woman and relating to your friends what you would do to her or whether you would even consider taking her out. Can also be used with innuendos (I'd like to check under her hood!)
Vinny: "Man, check out that fine honey over there!"
Pauly: "Damn son! I'd like to give her a pearl necklace and probe her holes!"
Tony: "You two need to quit bench fucking chicks and actually get some pussy!"