An animal or plant resulting from various interbreedings, especially a dog of mixed or undetermined breed. Offensive A person of mixed background or descent. Something that is a mixture or combination of elements:"Purists .. object that bordeaux is a mongrel because it mixes two, three or four grape varieties"(Hugh Johnson). Of mixed origin or character:"English has always been a mongrel tongue, a hybrid of arriving idioms"(Mark Abley). Offensive Being a person of mixed background or descent. Being a mongrel organism.