yellow card

Compare red card.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for yellow-card

yellow card

noun
  1. a card of a yellow colour displayed by a referee to indicate that a player has been officially cautioned for some offence
verb yellow-card
  1. (tr) to caution (a player) officially for some offence
adjective
  1. serving as a warning; intended to warna yellow card system is in place
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012