There are a number of definitions of the term Spinner when it comes to the game of dominoes.

On this site when I refer to spinners it will be referring to the small brass dot on the face of
the domino that allows the domino to spin freely when it is face down

A Spinner is commonly known as the double domino that starts the game
While playing the first double domino is the also called the spinner. This is because players can play off that domino in all directions. Since there are four sides to the domino you can play up to four directions from the double that starts the game.
Finally, there is also a game called SPINNERS
Spinner is the only dominoes game with wild dominoes that can be played as any number. A dynamic Double 9 Domino game plus 11 Spinner wild dominoes, Spinner is a great combination of other dominoes games, for a fun and exciting variation on traditional dominoes.
A quick video showing a logo that is particularly fun to spin on its SPINNER