[over.turn] vt (13c) 1: to cause to turn over: upset
2: invalidate, destroy ~ vi: upset, turn over
[2]over.turn n (ca. 1592) 1: the act of overturning: the state of being overturned
2: the sinking of surface water and rise of bottom water in a lake or sea that results from changes in temperature that commonly occur in spring and fall