Desi From Wiktionary, the Wikipedia dictionary

Desi (pronounced They-see) or Deshi (pronounced /they-she/)

Deshi means national as opposed to foreign. But for Indians abroad, it has become a term that mainly identifies an other fellow Indian. It is also applied to anything seeming very Indian(to a NRI-Non Resident Indian). Sometimes it is replaced with the more generic word Indian, but it is agreed upon that Desi brings the real flavour for the expression.

e.g., desi food refers to indian food like rice, dhal, chappati etc. desi dance can refer to the popular dances in the movies to punjabi dance, Bhangra to classical dances like Bharathnatya, Kuchipudi etc.

See also: ABCD