Chest hair on men, which is allowed to grow without shaving at the top of the chest (in any of various shapes), and shaved clean from well above the nipples down to the waistline.
A chestache allows a manly appearance in a partially unbuttoned shirt, but with a cleaner appearance below the chest whilst shirtless.
"I love running my fingers through his chestache."
"His handlebar chestache is oddly appealing, but I wonder how much wax it takes to do that"
2. I had to get waxed because of my chestache.