Q: How do snails fight?
A: They slug it out.

Explanation: “Slug it out” is an expression that means to fight.  Slug also means hit; if you slug someone, you hit someone.  In baseball, a slugger is someone who good at hitting the ball.

A slug is a living thing, similar to to a snail without a shell, that is often found in nature or perhaps in your garden.

This joke is funny because it plays with “slug” and “slug it out.” The slug slugs!

Here are some slugs slugging it out: