Chiefly Of a tooth: having a series of ridges that acts as a grinding surface; (originally specifically of a mammalian molar) having the crown folded at the sides, with the folds often crossing the crown. Of a dentition: consisting of such teeth.

Chiefly An animal with ptychodont or similar teeth; specifically a fossil shark of the Cretaceous family Ptychodontidae, with teeth that have a series of parallel folds adapted for crushing shells.