The Collaborative International Dictionary of English v.0.48:
Dam \Dam\, v. t. [imp. & p. p. Dammed (d[a^]md); p. pr. & vb.
1. To obstruct or restrain the flow of, by a dam; to confine
by constructing a dam, as a stream of water; -- generally
used with in or up.
I'll have the current in this place dammed up.
A weight of earth that dams in the water.
2. To shut up; to stop up; to close; to restrain.
The strait pass was dammed
With dead men hurt behind, and cowards. --Shak.
To dam out, to keep out by means of a dam.