Pearl/pɜːrl/ Definition 1 of 4Pro Tip 1/3Jewelry Item Pearls are highly valued in jewelry for their lustre and are often worn on formal occasions. She received a pearl ring for her wedding anniversary. Pro Tip 2/3Natural Formation Natural pearls form in oysters and other mollusks without human intervention. Divers hunted for natural pearls in the oyster beds. Pro Tip 3/3Cultured Pearls Most pearls in jewelry today are cultured or farmed by inserting a nucleus into shellfish. The cultured pearls in her bracelet were perfectly matched.