labile verb

Noun

 * 1)  A transitive verb, such as break, burn, boil, open, start, change, or assimilate, which may be used intransitively with the object of the action as the subject.
 * The verb 'break' is labile because it can be used both transitively: I broke the window, and intransitively: the window broke, and in either case the object undergoing the action of breakage is the window.