Someone who inhibits another person's game, thus lowering his or her chances to beat it up. Synonym of cock block or baller block.
George: "Hey honey. I have a favor to ask you."
Sally: "Anything for you, dear."
George: "Yeeeeah...so...would you mind putting a good word in for me with your little sister? I saw her sitting by the pool the other day in her bikini, and DAAAAAMMMN was she lookin' fine! I'd give anything to tear that ass up!"
Sally: "George, I'm your wife!"
George: "OK, fine, I'll let you hold the camera. While you're at it, tell your friend Tammy to come over too. I'd love to get her lipstick on my dipstick."
Sally: "Well I never!"
George: "Oh come on, honey, stop being such a stopcock! Hey, where's my dinner?"
Device in Chemistry or other science classes to restrict or allow the flow of liquid in a lab. However in OLCHS it is now the funniest word at the time. It is used in anyway that fits. Mostly used around immature teens such as myself.
Hey watch your stopcock its getting that liquid everywhere.