Wikipedia
Wašíču is the Lakota and Dakota word for people of non-indigenous descent, with derogatory connotations. It expresses the native population's perception of the non-natives' relationship with the land and the native population. Typically it refers to white people, but does not specifically mention skin color or race. The term "black wasichu" has been historically used to describe a person of African descent, and a Native American who adopted non-native ways could "make himself over into a wasichu".
Wasicun means "non-Indian". The Lakota word for "taking the fat" (wašin icu) is spelled and pronounced similarly, and it is used by natives in puns to refer to non-Natives who collectively rob tribes of their resources.
In Dakota, Wašicu also means the English language.