Explanation:

- A decorative object awarded for a victory is commonly called a trophy.

- Trophy is the most suitable one-word substitute for a decorative prize.

- Often made from metal, wood, or glass, it symbolizes achievement.

- Gift is a general term for something given willingly to someone without payment.

- Not typically associated with victory or competitive achievements.

- Present is synonymous with gift, meaning something given to someone on a special occasion.

- Like a gift, it does not specifically denote a victory prize.

- Crown refers to a ceremonial headpiece worn by royalty or a symbol of power and is less commonly used as a competitive prize.

- Occasionally, it might be used in contests, but it doesn't fit the general description asked in the question.