Tapering both ways from the middle: applied in botany to certain roots, as the radish, and in zoölogy to joints, organs, marks, etc., which are broadest in the middle and diminish regularly and rapidly to the ends.In ichthyology, having the dorsal and ventral contours symmetrical, and approximated to each other from a middle point toward each end, as the mackerel, tunny, and stickle back. Also fusate, fusoid.