Definitions of dam:

• noun:   female parent of an animal especially domestic livestock
• noun:   a barrier constructed to contain the flow of water or to keep out the sea
• noun:   a metric unit of length equal to ten meters
• verb:   obstruct with, or as if with, a dam

  Example: "Dam the gorges of the Yangtse River"

• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #12862)