A take on summer teeth. When you see someone with missing teeth, you can pronounce (behind their back of course) to your buddies, "she has winter teeth, winter the rest coming in"?
"She has winter teeth"
adj. Two above and three below. Describes a person who is missing more than a few teeth.
Kev: "Check that out, she's got winter teeth, two above and three below"
Erin: "She's obviously never heard of a toothbrush..."