A prize-winning thing or person has already won a prize. It is an adjective, and it likes to sit in front of a noun: a prize-winning novel, a prize-winning photographer, a prize-winning rose. It tells you a judge, a contest, or a show once picked this one as the best — or among the best. The tone is proud and public; people put it on book covers and posters. It does not mean 'valuable to me in my heart' (that is prized) and it does not mean 'winning right this second.' Though actually, after many years the prize may be forgotten by everyone except the poster, and we still say prize-winning.