Someone who has a heavy foot.
Saints accidentally step on a co-worker's foot. Her co-worker says "Dang, you got a lead foot. Ouch!"
Figurative term for a person who has a propensity to drive very fast.
Cop: "Alright, lead foot. You know how fast you were going back there?"
Person: "I'm sorry, sir, but-"
Cop: "You'll shut up if you know what's good for you. Now you were doing 75 in a 45, and I'm gonna throw the book at you."
Person: "Please, sir-"
Cop: "Quiet, boy. Don't you go anywhere, I'll be back."
(20 minutes later)
Cop: "Now you can either show up in court on this date, or pay this $300 fine. What were you in such a hurry for anyway?"
Person: "Taking my grandma to the emergency room. Now she's dead, you dumb fucking pig."
Cop: "Oh, sorry...uh, watch your speed."
(cop leaves and pulls into Krispy Kreme)