im not in the NY or Yeshivish world
where i hang out, i cant be rigorous in the definition, but i thought it referred to a certain group of boys (almost always its boys) who have thrown away almost all elements of Judaism, left their home and parents, are always in trouble, spend a lot of time with goyim and girls, drugs, and frequently run afoul of the law.
i see now that this is not the mainstream usage of this phrase