checker

Short definition from Wiktionary

Noun

1. 1
   One who or that which checks or verifies something.
2. 2
   One who makes a check mark.
3. 3
   The clerk who tallies cost of purchases and accepts payment.
4. 4
   One who hinders or stops something.
5. 5
   A playing piece in the game of checkers (British: draughts), or certain other table games such as backgammon.
6. 6
   A pattern of alternating colours as on a chessboard.
7. 7
   An individual square appearing in such a pattern.
8. 8
   The fruit of the wild service tree or chequer tree, Photinia villosa, syn. Sorbus terminalis

Verb

1. 1
   To mark in a pattern of alternating light and dark positions, like a checkerboard.
2. 2
   To develop markings in a pattern of alternating light and dark positions, like a checkerboard.