This literally means ‘father of moustache’ but in reality is just a convenient way to point out an unknown man with enviable facial hair, aka ‘that guy with the moustache’ in English. If you’re referring to a guy walking down the street wearing a red shirt, for example, he may similarly become “abu a7mar,” and sometimes the phrase has a comical, “I’m kind of making fun of this person but not really,” type of feeling.
For demonstrative purposes, let’s assume that one particular father of moustache is being a douche and blocking the street or something. You could say ابو شنب دا وقف الدنيا كلها which literally means “this father of moustache stopped the whole world!!!” –this is obviously a little dramatic and could be translated more accurately as “moustache guy is blocking everything.” Definitely know that this phrase doesn’t come up all that often, but I found it amusing, and it also provided a convenient excuse to post pictures of Nagy Shehata’s stash on the Internet.