Definition of: all fours

1. The four legs of a quadruped, or the arms and legs of a person.
2. Seven-up, a card game.
—to go (or be) on all fours
1. To move or crawl on all four limbs, as a baby.
2. To run smoothly, as a machine.
—to be on all fours with To present an exact comparison or analogy with.