It means climbing, rising, getting up, climbing, jumping or preparing to give them. Attack attitude of the beasts. Gain momentum or lean hard to attack or jump. Contracting the muscles of the limbs to jump.
It is a verb with origin in the adjective 'rampant', such as taking that attitude or posture, but also to the fact of climbing or crawling helping with the hands as claws.
Drag the soldiers on the ground.