sign language

Noun

sign language (countable and uncountable, plural sign languages)

1. (countable) Any of several natural languages, typically used by the deaf, in which words consist of hand shapes, motions, positions, and facial expressions.
   • It is safe to say that the academic world is now convinced that sign languages are real languages in every sense of the term.2000, Wendy Sandler, Diane Lillo-Martin, edited by Mark Aronoff and Janie Rees-Miller, The Handbook of Linguistics
2. (uncountable) The sign language (sense 1) that is used locally or that is mistakenly believed to be the only one.
   • I'm taking night classes to learn sign language.
3. (uncountable) Sign languages (sense 1) considered collectively.
   • There are some unique properties found in sign language compared to spoken language.
4. Communication through gestures as a substitute for language, for example, between monks under a vow of silence or during trade amongst different linguistic groups.
   • Even Maxwell the trader, who has been most among them, is compelled to resort to the curious sign language common to most of the prairie tribes.1847, Francis Parkman, The Oregon Trail