1. Attending a party uninvited or after asking for an invite.

2. Show up at a party uninvited or self invited and do something remarkable.
Mike crashed the new years eve party in his alligator suit. In many cases nothing remarkable is planned or happens when someone claims to crash a party.
by Anonymous (not Jason Legako) January 31, 2015
Attend a party without being invited. You just show up. It may be a party thrown by someone you know or a complete strangers house. Sometimes people don't mind that you came to their party, but sometimes, your presence will be unwelcome and you may be asked to leave. The fun of it is you don't know until you get there what the reaction will be. If you crash the party, be ready to accept the consequences.
Dude, there is a jamming party down the street! Let's go crash the party!
by Happy Go Lucky November 12, 2013
When one unintentionally tags along or goes to an event that one may not be wanted at. One feels like the proverbial fifth wheel and like one is intruding and that one is not wanted. A very awkward situation.
Greg: I ended up going out to eat with Sarah's family last night.
Jeff: Really?
Greg: yeah, the problem it that it was a welcome home dinner for her sister.
Jeff: man, you totally gate crashed their cocktail party.

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Sarah: Greg gate crashed my family's cocktail party!
Georgette: bummer.

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Georgette: friends don't let friends go around gate crashing a cocktail party.
Jeff: ...awkward...
by Georgette January 1, 2006
Ironic, a non-party which develops in virtual worlds when avatars are thrown awkwardly together at random due to being redirected to a hub site during a teleport malfunction.
I was trying to teleport up to my skybox and I wound up at a crash party with three giant lizards and a naked gnome.
by kerfoofle November 7, 2010