Wiktionary
n. A form of locomotion of some primates in which they move on all fours with pressure being taken by the knuckles.
Wikipedia
Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles. In technical terms, knuckle-walking is locomotion with the manus (Latin for hand) distally flexed on contact with the substratum.
Gorillas and chimpanzees use this style of locomotion as do anteaters and platypuses.
Anthropologists once thought that the common ancestor of chimpanzees and humans engaged in knuckle-walking, and humans evolved upright walking from knuckle-walking: a view thought to be supported by reanalysis of overlooked features on hominid fossils.
Since then, scientists discovered Ardipithecus ramidus, a human-like hominid descended from the common ancestor of chimpanzees and humans. Ar. ramidus engaged in upright walking, but not knuckle-walking. This leads scientists to conclude that chimpanzees evolved knuckle-walking after they split from humans 6 million years ago, and humans evolved upright walking without knuckle-walking.
Usage examples of "knuckle-walking".
He selected a direction—east, as it happened, into the light of the rising sun—and, his gait a mixture of clumsy knuckle-walking and upright sprinting, he ran back and forth along a trail that led that way, glancing back at Capo for approval.
He could not sweat, and his knuckle-walking gait, effective for clambering around the complex, crowded environment of the forest, was inefficient here.
Their fingers and toes remained long and curved to help grab hold of tree trunks, and their legs were a peculiar compromise between the needs of knuckle-walking tree climber and those of biped.
One by one, timidly, walking upright or knuckle-walking, the rest of the troop followed her.
Grant edged toward the pen's entrance, Sheena growled and glared at him, then took a knuckle-walking step toward him.
His arms, however, were of normal length: he used them to aid his movements, knuckle-walking like a chimpanzee.
The Vomnin—long-armed, knuckle-walking quasihumanoids with bronze skin and wide, flat faces—were the scientists and engineers.
We're not gonna come knuckle-walking out of here tonight like Shasta ground sloths, you wave?