Форшмак
This is a Russian insult affecting honor and dignity. Meaning that a man had contact with someone else's penis with his mouth or had oral sex with girls. It is actively used criminal community in regions far from the capitals. Closer to the capitals, it is not so easy to stumble upon this word, it becomes obsolete. Because of the mentality - this swear word was hurted manhood.
Не пей с этим мужиком с одного стакана!
Почему?
Он форшмак.
(don't drink with this guy from the same glass!
why?
Because he is Forshmak.)
Почему?
Он форшмак.
(don't drink with this guy from the same glass!
why?
Because he is Forshmak.)