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."
The word 'Scumtard' originated in 2009 by a Sir Smalbert. However, Matt Damon had trouble reading the word in the Bourne 4 movie script and people are now pronouncing it as 'Scum-tahd".
Yo look at Mainthow that scumtahd... I heard he was writing Idiots for Dummies.
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