Dom"i*no (?), n.; pl. Dominos or (esp. the pieces for a game) Dominoes (#). [F. domino, or It. dominò, or Sp. dominó, fr. L. dominus master. The domino was orig. a hood worn by the canons of a cathedral. See Don, Dame.] 1. A kind of hood worn by the canons of a cathedral church; a sort of amice. Kersey.

2. A mourning veil formerly worn by women.

3. A kind of mask; particularly, a half mask worn at masquerades, to conceal the upper part of the face. Dominos were formerly worn by ladies in traveling.

4. A costume worn as a disguise at masquerades, consisting of a robe with a hood adjustable at pleasure.

5. A person wearing a domino.

6. pl. A game played by two or more persons, with twenty-eight pieces of wood, bone, or ivory, of a flat, oblong shape, plain at the back, but on the face divided by a line in the middle, and either left blank or variously dotted after the manner of dice. The game is played by matching the spots or the blank of an unmatched half of a domino already played Hoyle.

7. One of the pieces with which the game of dominoes is played. Hoyle.

• A rectangular block divided into two squares, each having 0 to 6 dots (as in dice), used in the game of dominoes.
  
• (politics) A country that is expected to react to events in a neighboring country, according to the domino effect
  
• A masquerade costume consisting of a hooded robe and a mask covering the upper part of the face.
  
• The mask itself.
  
• The person wearing the costume.
  
• (geometry) A polyomino made up of two squares.