Gabacho is a slur used to describe Whites in a derogatory way. Connotes "imperialist"; used by Mexicans and Mexican-Americans; apparently originated in Spain to refer to French.
The word Gabacho is a racial slur that has been used historically to degrade and dehumanize whites. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to whites. If you are unsure about whether or not it is appropriate to use the word Gabacho, it is best to err on the side of caution and avoid using it in any situation.