What does "dam" mean?

Additional senses

1. 2.A barrier to prevent the flow of a liquid; esp., a bank of earth, or wall of any kind, as of masonry or wood, built across a water course, to confine and keep back flowing water.
2. 3.(Metal.) A firebrick wall, or a stone, which forms the front of the hearth of a blast furnace. Dam plate (Blast Furnace), an iron plate in front of the dam, to strengthen it.
3. 4.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.
4. 5.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.