yellow card 
noun
(In soccer and some other games) a yellow card shown by the referee to a player being cautioned: Eddis was shown the yellow card for a late tackle on Candlish...Compare with red card.
- The referee bought his yellow card out and Gascoigne was out of the final were England to make it through.
- What is the difference between a yellow card in hockey and a yellow card in soccer?
- He could not be trusted, they said, because he had clocked up one red card and 20 yellow cards in the past two seasons.
verb
(yellow-card) [with object] (Of the referee) caution (a player) by showing a yellow card.Symes got caught up in a brief spat with right back Adrian Harper which saw both players yellow-carded....
- English referee Roy Maybank warned Hayes and Parker, then yellow-carded Kelly.
- At this stage the referee yellow-carded both scrum halves and a Pontefract forward for a professional infringement.