subdialect

noun

sub·​di·​a·​lect ˌsəb-ˈdī-ə-ˌlekt 

variants or sub-dialect

plural subdialects or sub-dialects

: a dialect of a language that is a regional subvariety of a more widely spoken dialect

Today Aleut is a single language with two main dialects, Western (Attuan and Atkan subdialects) and Eastern.

—William W. Fitzburg & Aron Crowell

Word History

First Known Use

1642, in the meaning defined above