What is "to dam out"

Dam \Dam\, v. t. [imp. & p. p. Dammed (d[a^]md); p. pr. & vb. n. Damming.]

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.
   --Shak.

   A weight of earth that dams in the water.
   --Mortimer.

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.