Noun- when a man does not have a fully developed mustache, instead he has peach fuz like hairs, that are usually dirty, on his upper lip. Most commonly seen on mexicans, 11-13 year old boys, and people who are down right hideous.
wow hes been trying to grow out a mustache for weeks and all its turnd out to be is dirty scumstache
A mustache that is not fully grown in yet, and is still growing, so the hairs are spread apart. Scumstash mostly applies to mexicans who are dirty, but can be applied to noobs with a mustache thats dirty.
Crystal: "Lucas, I love your scumstash, it's so dirty."
Lucas: "Thank you ese."
James: "Yo scumballs, get you and your shitstash outta here."