Definition of Christmas cactus in English:

Christmas cactus

noun

  • A Brazilian cactus with branching stems of glossy green, flat, broad, tooth-edged sections, the tips of which bear long flowers, typically red or pink, with recurved outer petals. Christmas cacti are widely cultivated as houseplants.

    • ‘Every fall, my Christmas cactus displays a spectacular profusion of blooms on a covered patio in San Mateo, California.’
    • ‘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.’
    • ‘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.’
    • ‘The best flowers to give at Christmas time are orchids, holly, poinsettias, and the Christmas cactus as well as any red flower.’
    • ‘And remember to get your poinsettias and your Thanksgiving and Christmas cacti ready for well-timed holiday color.’

Origin

So named because it flowers at about the northern midwinter.