sign language

noun4

1. •
   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
2. •
   The sign language that is used locally or that is mistakenly believed to be the only one.

   • I'm taking night classes to learn sign language.
3. •
   Sign languages 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