1. all four limbs or extremities; the four legs or feet of an animal or both arms and both legs or both hands and both feet of a person: The cat rolled off the ledge but landed on all fours.
2. ( used with a sing. v. ) Also called high-low-jack, old sledge, pitch, seven-up . Cards. a game for two or three players or two partnerships in which a 52-card pack is used, the object being to win special scoring values for the highest trump, the lowest trump, the jack, the ace, the ten, and the face cards.
3. on all fours ,
a. in conformity with; corresponding exactly with.
b. (of a person) on the hands and feet, or the hands and knees: I had to go on all fours to squeeze through the low opening.
[ 1555-65 ]