A scraggly mustache/goatee that has many different colored hairs in it (brown, blond, red, grey, etc), particularly in patches, resembling the fur coat of a mongrel, or mutt.
May or may not be disgusting in appearance.
That guy with the shaved head and goatee looked all hardcore until I saw his muttstache. Now he just looks like a redneck hillbilly skinhead reject, who likes country music, shotguns, and trucks with large tires on them.
Thanks for applying to the open management position. After careful consideration of your qualifications, we have decided to pursue a candidate who did not have a muttstache, and who would not pass for Jeff Foxworthy from a distance.
There ain't NUTHIN more 'Merican then.. coun'try myusic, bein listened to on a boombox by a guy with an awesome muttstache.
The West Virginia politician's constituents admired him for his honesty, charisma, and his neatly groomed muttstache.