When the mustache starts hanging over the top lip, one needs to perform a stache-tuck by tucking the overhanging mustache fibres in underneath the main body of mustache to make the mustache more presentable, neater and defined.
Before John's hot date with Kelly, he executed a stache-tuck. This proved useful as it neatened out his mustache and kept the mustache hairs out of his and Kelly's mouth while they were kissing.
by Fook-ST@R April 13, 2014