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34.
To interfere with a male's attempt at talking to a female or the other way around, especially if it involves sex. This is mainly performed by obstructing the path between the male and the female. Normally, the person that's doing the "cockblocking," has the intention on talking to the male/female.
BABY MAMA: I'm talking to this guy now name Terrence. He's a nice and comical guy.

BABY DADDY: You gonna have to cut that man off, I don't care if he's nice or not, he better not be in the picture.

BABY MAMA: Oh, now you wanna cockblock for the simple fact that I moved on without your sorry ass.
by Mr. Terrence L. Trezvant April 04, 2008
 
1.
One who prevents another from scoring sexually.
Trudy and Dan frequently had time alone but her cockblocking roommate ruined any chances they had to have sex.
by Miss Priss April 13, 2003
 
2.
1. To prevent a male friend or associate from getting some action.

2. Any such attempt to prevent a male friend or associate from getting some action.
1. Damn, Johnny just totally cockblocked his roommate. Ass.

2. OK, Isaac's making his move on Clarisse in the living room, and the game is on in fifteen minutes. We're going to have to attempt a cockblock.
by Jake April 12, 2003
 
3.
1.) To interfere with someone who is getting acquainted with, conversing with, or hooking up with a member of the opposite sex

2.) A motor vehicle maneuver, usually done by insecure twenty-something males (who think that everybody wants to race them) and other ignorant people, designed to prevent someone from changing lanes in traffic
1.) At the club, Sal was was about to get Lisa's phone number, when Nathan came up cock-blocked him by asking him if he found a job yet. He made it even worse when he reminded Sal that they had to hurry up and catch the last bus home. Lisa rolled her eyes and walked away.

2.) I realized that my exit was coming up so I began to change lanes, but that ricer cock-blocked me

3.) The traffic on the highway was hell, mostly because of that soccer mom driving the minivan in the far left lane, pacing and matching speeds with the semi in the middle lane. She cock-blocked us all.
by TheGrandInquisitor January 24, 2005
 
4.
1.The act of obstructing one person's advances towards another.
2.A situation that obstructs; an obstacle
3.An act of ill etiquette in which a male is speaking to one female in a group of females, and the alpha female creates a disruptive environment.
She is cockblocking you bro.
by The GIMP September 23, 2003
 
5.
a person who interferes with one's sexual intentions with another person
Randy was a cockblock because he told Jaime that this guy she knew was just using her for sex.
by Bob Mastuff October 13, 2003
 
6.
(n.) one who prevents another from getting "play", "poontang", etc.
(v.) any action that impedes or stalls another's "game", "mack", or "pimp manuver"
(n.) I was dancing with this girl, when this cock-block stepped in between us and started grinding with her.
(v.) I had finally convinced Susan to go to my friend's keg party with me, when my Dad cock-blocked me by taking away my car keys.
by MCKREWGA September 13, 2003
 
7.
1. To interfere with a man's attempts to seduce a woman.

2. abbr. Cockblocker(n.)
I was putting the move on this chick and Ralph showed up and cockblocked me.
by Anonymous February 06, 2003