bulb

bulb

noun \ˈbəlb\

Definition of BULB

1

: a rounded dilation or expansion of something cylindrical <the bulb of a thermometer>; especially : a rounded or pear-shaped enlargement on a small base <the bulb of an eyedropper>

2

: a rounded part: as a : a rounded enlargement of one end of a part—see bulb of the penis, bulb of the vestibule, end bulb, hair bulb, olfactory bulb b : medulla oblongata; broadly : the hindbrain exclusive of the cerebellum c : a thick-walled muscular enlargement of the pharynx of certain nematode worms