Anatomy. the socket in the hipbone that receives the head of the thighbone.
Zoology. any of the suction appendages of a leech, octopus, etc.
Origin of acetabulum
1660-70; < Latin: hip socket, cup-shaped part of a plant (Pliny), literally, small cup, orig. for vinegar, equivalent to acēt(um) vinegar + -ā- by analogy with verbal derivatives (cf. vocable) + -bulum suffix denoting instrument or vessel