1. Someone who deprives someone of something or who holds something out on his friends (doesn't throw them a bone). Derived from the "Old Mother Hubbard" nursery rhyme in which mother Hubbard went to her cubbard to get her poor dog a bone. But when she got there the cubbard was bare, and so her poor dog had none.

Basically a brother who won't hook a brother up.

2. A G-rated substitute for M.F.

Got the covid-19 vaccine

not having any medical : see also bummer and medical emergency