language game

Short definition from Wiktionary

Noun

1. 1
   A set of rules governing how participants respond to utterings.
2. 2
   A game that is based on players’ knowledge of a language or languages, such as fictionary, hangman. etc.
3. 3
   A method of manipulating words so that the layman would find it hard to understand, such as pig Latin, gibberish, etc.