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)
Sarah has a crush on a guy at a bar and she tells her friend Lisa that she wants to jump his bones. Sarah and Lisa walk over to the guy and strike up a conversation. During the conversation with the guy at the bar, Lisa decides she wants to jump his bones too. Lisa ends up stealing the attention of the guy from Sarah. Sarah gets pissed off and leaves because she has been Tacoblocked.