Definitions

1. noun

either of the two lower or posterior parts of the body in certain invertebrates, such as a worm or a caterpillar, or any of the two posterior parts of the body in certain other animals, such as an insect or a frog

“The caterpillar’s crura were weak and unable to carry its weight.”

2. noun

the two posterior extremities of the body in certain birds, such as the ostrich, emu, and rhea, which are used for standing and walking, but not for running

“The ostrich uses its crura to balance and walk on land.”