Playing With / Hiding Behind the Language Barrier

Basic Trope: Characters use a language they know but a third party does not, in order to exclude them from the conversation.
  • Straight: Alice, Bob, and Claire speak Language A, but Alice and Bob speak Language B to prevent Claire from understanding them.
  • Exaggerated: Alice and Bob have most of their conversations in languages chosen to prevent present company from understanding.
  • Downplayed: Alice and Bob talk a little in Language B in the middle of a conversation that is otherwise entirely in Language A.
  • Justified: Alice and Bob are foreigners in Claire's home country, where Language A is the official language, and don't speak Language A very well, find it frustrating, and see no reason to speak it unless they must. The fact that they don't want Claire to understand them is only a bonus.
  • Inverted: Alice and Bob know that Claire is listening in, and deliberately feed her false information. So they speak in Language A.
  • Subverted: Claire also knows Language B and understands the conversations that Alice and Bob wanted to keep secret from her.
  • Double Subverted:
    • Claire doesn't know Language B well enough to understand the conversation fully.
    • Alice and Bob speak in a dialect wherein Claire is inexperienced, to the same effect.
  • Parodied: Language B is simply Language A with "comedy acksent forreen."
  • Zig Zagged: Claire knows Language B. She can't understand all of it, but she can infer that Alice and Bob are discussing something about her and is hurt by it, assuming it is negative. As a result, she is completely blindsided when Alice and Bob reveal that they discussed the possibility of teaching her Language B. Only it is because they intend to include her in conversations they have about other people in public.
  • Averted: Alice and Bob don't speak in Language B.
  • Enforced: ???
  • Lampshaded:
    Alice: We can't let Claire find out about this, Bob.

    Bob: It's a good thing she doesn't know Language B, Alice!
  • Invoked: Alice and Bob take classes in a language they know Claire does not speak.
  • Exploited: ???
  • Defied: Alice and Bob can speak Language B, but choose not to because they don't want to act like they are keeping secrets from Claire.
  • Discussed: ???
  • Conversed: ???
  • Implied: Alice and Bob speak less comprehensibly when Claire is around than at other times.
  • Played for Laughs: Alice and Bob tell jokes in Language B. If Claire could understand the jokes, she might or might not have a case of Humor Dissonance towards them.

I'm sure the people talking in that language I don't know are discussing Hiding Behind the Language Barrier
http://tvtropes.org/pmwiki/pmwiki.php/PlayingWith/HidingBehindTheLanguageBarrier