WordNet
n. a joke at the expense of some ethnic group
Wikipedia
An ethnic joke is a remark attempting humor relating to an ethnic, racial or cultural group, often referring to an ethnic stereotype of the group in question for its punchline.
Ethnic jokes reinforce ethnic stereotypes and sometimes lead to calls for violence.
Perceptions of ethnic jokes are ambivalent. Many find them racist and offensive. On the other hand, jokes poking fun an one's own ethnicity are sometimes considered acceptable but Christie Davis challenges this notion of there being an innocuous ethnic joke. The perceived damage to the ethnic group can be of great concern as when the ethnic Polish jokes became so common in the 1970s the Polish Ministry of Foreign Affairs approached the U.S. State Department to complain.
Usage examples of "ethnic joke".
He was out of patience with this fool, who was more a broad ethnic joke than a human being.
Even Dick Artemus, the undeniably charismatic governor, had managed to repulse Desie with a distasteful ethnic joke within moments of being introduced.