Definition of Christmas cactus in English:

Christmas cactus

noun

  • A South American cactus with flattened segmented stems and red, pink, or white flowers, grown as a houseplant.

    • ‘You'll be glad to hear that my Christmas cacti are now dripping with pink buds and the geraniums on my frost-free balcony continue to bloom spectacularly.’
    • ‘While poinsettia is the most popular, a Christmas cactus in full bloom is a great gift and easy to care for once the flowers have faded.’
    • ‘Every fall, my Christmas cactus displays a spectacular profusion of blooms on a covered patio in San Mateo, California.’
    • ‘And remember to get your poinsettias and your Thanksgiving and Christmas cacti ready for well-timed holiday color.’
    • ‘The best flowers to give at Christmas time are orchids, holly, poinsettias, and the Christmas cactus as well as any red flower.’

Origin

So named because it flowers at about the northern midwinter.