When someone has a tooth that seemingly grows in front of a row of teeth in an obtrusive and obvious way. Generally the misplaced teeth are so unsightly it comes as a shock when the person's mouth opens. Jewels teeth are a mild example.
That chick was hot, but when she smiled she totally had a lead blocker.
A large person you follow behind to get to the front of a crowded bar. Similar to how a running back follows an offensive lineman in football.
Chris: I've been waiting in this line for like 10 minutes, how'd you get drinks so fast?
Geo: I used Duke's giant girlfriend, Stacey as my lead blocker to push to the front.
Chris: She's quite the battering ram.