Real Dictionary

Tex-Mex
You use Tex-Mex to describe things such as food or music that combine typical elements from Mexico and the south-western United States.

Tex-Mex in American English
characterized by both Mexican and southwestern American (esp. Texan) elements, influences, etc.
adjective: of or pertaining to aspects of culture that combine Mexican and Texan or southwestern U.S. features, esp. aspects of culture developed in southern Texas based on or influenced by Mexican elements
noun: a form of Mexican Spanish having elements of English and spoken near the border of Texas and Mexico, esp. Mexican Spanish as spoken in Texas

Tex-Mex in British English
adjective: of, relating to, or denoting the Texan version of something Mexican, such as music, food, or language