1. A person who attends a party, event, or venue without being invited or without paying admission
The security guard caught a gatecrasher trying to sneak into the concert.
O segurança apanhou um invasor de festas tentando entrar no concerto.
2. Someone who gains unauthorized access to a restricted area or private event
Several gatecrashers managed to get past the door staff at the exclusive party.
Vários invasores conseguiram passar pela equipa de porteiros na festa exclusiva.