1. One of the five radial areas on the undersurface of the starfish and similar echinoderms, from which the tube feet are protruded and withdrawn: "These ambulacra usually have rows of locomotive suckers or tentacles, which protrude from regular pores of starfish so they can move (walk) around."
2. The suckers on the feet of mites: "Mites use ambulacra as a means of walking on and hanging on to their victims."