yellow card

plural yellow cards

1. hobbiesA yellow-coloured card, shown to a player (especially in association football) as a caution that he or she has committed a flagrant foul; a further such foul would result in a red card.
2. medicineOne of various yellow-colored cards used to verify the healthiness, vaccination status or other medical info of travelers.
3. UKmedicineA form to record safety concerns and adverse reactions to medicinal drugs.
4. attributiveoftenA card sent out by a travelling dance or theatre company to request temporary personnel from a local labor union.

   Some large modern dance companies, most large ballet companies, and most large theater companies also require union crews. These are called yellow card companies.

   1991, M. Kay Barrell, The technical production handbook

   1 more example

   Each local union has a separate number; New York was the first so they are Local One. Chicago is Local Two. A yellow card (they have been printed on yellow cardstock since time began) is sent out telling how many hands will be required in in each department for the load-in, load-out, and for the run of the show.

   2014, John Ramsey Holloway, Illustrated Theatre Production Guide, page 6

5. historicalA yellow ticket.
6. historicalA card given to British Army personnel during The Troubles.