Gelatin/ˈdʒelətɪn/ Definition 1 of 3Pro Tip 1/3Cooking Thickeners Gelatin is commonly used to thicken liquids into gels. She stirred the gelatin into the fruit juice for her homemade jelly. Pro Tip 2/3Dietary Restrictions Some people avoid gelatin for dietary or religious reasons since it's derived from animals. The vegetarian pudding was made without gelatin. Pro Tip 3/3Setting Process Gelatin needs to be dissolved in warm water and cooled to set properly. After mixing the gelatin in warm water, she refrigerated it to set her mousse.