echi·no·cactus \ ̷ ̷ ̷ ̷ ̷ ̷ at echino-+\noun Etymology: New Latin, from echin- + Cactus 1.capitalized: a large genus of globular or cylindrical strongly ribbed and usually very spiny cacti that occur from the southwestern United States in Brazil 2.: any plant of the genus Echinocactus