1 : the ability to raise the working leg high in the air; "the dancer was praised for her uncanny extension"; "good extension comes from a combination of training and native ability"
2 : the most direct or specific meaning of a word or expression; the class of objects that an expression refers to; "the extension of `satellite of Mars' is the set containing only Demos and Phobos"
3 : an educational opportunity provided by colleges and universities to people who are not enrolled as regular students
4 : the spreading of something (a belief or practice) into new regions
