Definitions of domino:

• noun:   a small rectangular block used in playing the game of dominoes; the face of each block has two equal areas that can bear 0 to 6 dots
• noun:   a mask covering the upper part of the face but with holes for the eyes
• noun:   a loose hooded cloak worn with a half mask as part of a masquerade costume
• noun:   United States rhythm and blues pianist and singer and composer (born in 1928)
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #14350)