1. A condition that occurs when ones hairlines have gradually grown past their natural territory and begin to encompass as well as fuse with, the hair of other regions on the body creating a solid, suit-like appearance.
2. When ones beard grows in to their chest hair, down the happy trail, around the junk, under the taint, in the crack, up the back, and finally arriving at the hair on the back of the head.
"Dude you better watch your hairlines, slack off for a bit and you'll end up with a Mexican Backstrap."