1. a variety of a language that is associated with a particular geographical region, social class, or ethnic group and has its own characteristic words, grammatical forms, and pronunciation. Dialects of a language are generally mutually intelligible. Compare accent; register.

2. among nonhuman animals, a variant of the standard form of communication that is specific to a population or a geographical region. For example, cardinals in different parts of North America have regional differences in song. —dialectal adj.