Yes, dominos is a Scrabble word!

Noun

1. Any of several games played with small rectangular blocks

2. United States rhythm and blues pianist and singer and composer (born in 1928)

3. A loose hooded cloak worn with a half mask as part of a masquerade costume

4. A mask covering the upper part of the face but with holes for the eyes

5. 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