When you and another person are squished together so that your boob is against their armpit, or vice versa. Typically used when standing in a crowded place, like the student section at a football game.
The underside of large tits. Functioning much like an armpit, the meeting of two layers of skin forms a crevice or pit, capable of accumulating sweat. Fortunately, tit pits are generally not hairy.
This double Dbra is cotton lined, to wick away sweat from your tit pits.
The area underneath a tit. Only in larger breasted women, and much like the sister area under the arm "armpit," the tit pit is hidden in the fold of a hanging boob.