The term 'SUBJECT OF A DONOR CARD' can be summarized as the person who is donating an ORGAN, such as a kidney or heart. The crossword solution for this term is 'ORGAN', which is a five letter word. An ORGAN donor card is a document that states a person's willingness to donate their organs after death. This document is important because it allows medical professionals to make sure that the donor's wishes are respected and that their organs are used to help save the lives of others.