In the broad sense of the term, i would say it’s someone who follow the hashkafah of the yeshivot litvish. A chassid would be called chassidish, even if he went to the same yeshivah.
I assume that they called you yeshivist because you were tzitzit outside and black kippah or black hat.
If Boro Park calls you goyish, tell them: maybe a sheigetz but a kosher sheigetz”.