When a date is ruined or becomes less romantic due to a third person such as a uninvited friend or family member.
Merry's date was ruined when she found her dad being a date crasher.
When your main chick let's you sleep with your side chick on purpose and walks in to join without asking.
Damn she is such a pussy crasher
He’s a slimy wee gash crasher . Watch him around your girlfriend