a. Closed from beneath. [ 1913 Webster ]

Undershut valve (Mach.), a valve which shuts by being lifted against a seat facing downward. Knight. [ 1913 Webster ]

a. 1. (Zool.) Having the lower incisor teeth projecting beyond the upper ones, as in the bulldog. [ 1913 Webster ]

2. Moved by water passing beneath; -- said of a water wheel, and opposed to overshot; as, an undershot wheel. [ 1913 Webster ]