- (botany) Any member of the family Cactaceae, a family of flowering New World succulent plants suited to a hot, semi-desert climate.
- Any succulent plant with a thick fleshy stem bearing spines but no leaves, including euphorbs.
In modern English, the term cactus properly refers to plants belonging to the family Cactaceae. With one exception, all are native to the New World (the Americas). The sole exception is Rhipsalis, a jungle epiphyte found in tropical Africa, Madagascar, and Sri Lanka, as well as North and South America. Informally, cactus is used to refer to any stem succulent adapted to a dry climate, notably species from genus Euphorbia with forms reminiscent of Cactaceae. To be precise, these succulents are correctly described as "cactoid" or "cactiform" unless they are actual members of the Cactaceae.
- (member of Cactaceae): succulent
cactus (not comparable)
- (Australia, New Zealand, slang) Non-functional, broken, exhausted.
- 2009, Will Chaffey, Swimming with Crocodiles: An Australian Adventure, page 108,
- ‘It′s cactus,’ Rod, the helicopter pilot, said at the sound of the piston ring shattering.
- Hyphenation: cac‧tus
cactus m (plural cactus)
- “cactus” in le Trésor de la langue française informatisé (The Digitized Treasury of the French Language).
- cactus in Charlton T. Lewis & Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
- “cactus” in Félix Gaffiot (1934), Dictionnaire Illustré Latin-Français, Paris: Hachette.