1. Someone who knows a lot of languages and doesn't use them.
2. Someone who starts learning a lot of languages, but gets bored with them after a few weeks.
1. Bob knows over 12 languages, and I've never heard him speak any other language apart from English. What a language slut.
2. Faye is such a language slut. She starts all these languages, but gets bored with them after only a few days.