di·glos·si·a 
(dī-glôsē-ə, -glŏsē-ə)
(dī-glôsē-ə, -glŏsē-ə)n.
The use of two markedly different varieties of a language in different social situations, such as a formal variety at work and an informal variety at home.
[From Greek diglōssos, speaking two languages : di-, two; see DI-1 + glōssa, tongue, language.]
di·glossic adj.