Continuity mistake: In 1955, when Marty shows Doc the flux capacitor, he points the flashlight in different directions between shots (first at Doc, then the flux capacitor). (00:51:35)
Continuity mistake: As Lorraine's family watches "The Honeymooners" around the dinner table, a round pillow on the sofa nearest the lamp repositions itself. (00:46:05 - 00:47:30)
Continuity mistake: As Marty watches George pedal away from the café, the amount of sunlight cast on the town square decreases greatly between shots. (00:41:00)
Continuity mistake: While Marty is talking with Jennifer in the square he is holding a tape case in his left hand which disappears in the next shots.
Answer: It's a way of saying "scram" or "get lost." But Biff is so dim, he doesn't realize he's saying it wrong; the expression is "make like a tree and leaf", with the joke being that "leaf" is meant to sound like "leave."
Cubs Fan ★