cy·clo·stome (sī'klə-stōm') n. Any of various primitive eellike vertebrates of the class Agnatha, such as a lamprey, lacking jaws and true teeth and having a circular, sucking mouth.
[From New Latin Cyclostomī and Cyclostomata, class names : cyclo- + Greek stoma, stomat-, mouth.] cy·clos'to·mate' (sī-klŏs'tə-māt', -mĭt), cy'clo·stom'a·tous (sī'klə-stŏm'ə-təs, -stō'mə-) adj.