龙珠 has two very different meanings. Its most common sense is the proper noun for the iconic Japanese manga and anime franchise 'Dragon Ball' (ドラゴンボール), a household name in Chinese-speaking pop culture. It also refers to an obscure Solanaceae plant, Tubocapsicum anomalum (devil's tomato), but this usage is rare and unlikely in everyday conversation. Be aware that without context, 龙珠 almost always means Dragon Ball.