Definition of "checker"

checker¹

/ˈtʃɛkə/

noun
plural checkers
1. One who or that which checks or verifies something.
  Quotations
  So, keep in mind that Microsoft Word’s Spelling tool is as much a “typo” tool as a checker of spelling.
  1992, Neil J. Salkind, Applying Macintosh: Solutions, Ideas, and Tools, Macmillan Publishing Company, page 205
2. One who makes a check mark.
  Quotations
  "Essentially," said a senior vice president of the FHLBB of Dallas, "we were checkers of boxes."
  1989, M. Manfred Fabritius, William Borges, Saving the Savings and Loan
3. The clerk who tallies cost of purchases and accepts payment.
  Quotations
  Bud Brown said something to the checker he was supervising; she had been craning around to see what was happening. She flushed and began to run her calculator again.
  1980, Stephen King, The Mist
4. One who hinders or stops something.

checker²

/ˈtʃɛkə/

noun
plural checkers
1. A playing piece in the game of checkers (British: draughts).
2. A pattern of alternating colours as on a chessboard.
3. An individual square appearing in such a pattern.
verb
third-person singular simple present checkers, present participle checkering, simple past and past participle checkered
1. (transitive) To mark in a pattern of alternating light and dark positions, like a checkerboard.
2. (intransitive) To develop markings in a pattern of alternating light and dark positions, like a checkerboard.

checker³

/ˈtʃɛkə/

noun
plural checkers
1. The fruit of the wild service tree or chequer tree, Photinia villosa, syn. Sorbus terminalis