A crasher is someone who shows up uninvited to an event, especially a party or celebration. When someone crashes a wedding, birthday party, or school dance without an invitation, they're being a crasher. The word suggests sneaking in where you don't belong, trying to blend in and enjoy the fun even though you weren't asked to come.

Sometimes crashers are harmless: maybe they heard about a great party and figured no one would mind one extra person. But crashing can also be rude or disruptive, especially at events where the hosts planned carefully for a specific number of guests or want to celebrate with particular people. A wedding crasher might eat food meant for invited guests or take up a seat at a carefully arranged dinner.

The word can describe other kinds of unwelcome arrivals too. Someone who interrupts a private meeting they weren't invited to might be called a crasher. In old movies, you might hear about “gate crashers” who sneak past security at exclusive events.

Being invited matters because it shows respect for the host's plans and wishes. When you're invited somewhere, you know you're genuinely wanted there.