Situation 1: When a girl is 'cock blocked' by her friend when that girl totally had dibs on the guy at the beginning of the night.
Situation 2: When a girl wants to nail a guy and she can't because the guy doesn't want to nail her. (similar to bluewalls)
person b: "crap, i think i just ate it!"
person a: "dude, you fucking just taco-blocked me!"
person 1: "Dude we got you taco bell on our way here"
person 2: "Did you remember to order it with no fiesta?"
person 1: "Oh crap, I forgot"
person 2: "Dude, you totally taco-blocked me!"
person a: "ooh! order me a 5$ box!"
person b: "okay dude"
person a: (passes out, too drunk to eat)
person b: "you passed out, i ate your tacos"
person a: "dammit! I just got completely taco blocked!"