Foutre can mean two things:
1. The verb "foutre": je fous, tu fous, etc... is slang for "faire" (to do, see Ex 1a) or "mettre" (to put, see Ex 1b).
2. As a noun, refers to male's cum (sperm).
There are also awesome french expressions: "Va te faire foutre" (maybe a synonym for "fuck you") and also "J'en ai rien a foutre" or "Je m'en fous (completement)" (I (really) don't give a shit).
1a. "Qu'est-ce que tu fous ?" What are you doing?
1b. "Elle aime quand je lui fous mon doigt dans la chatte" She likes it when I stick my finger in her pussy.
2. "Il y avait du foutre plein le lit" There was come all over the bed.