Definition of coccyx in US English:


nounPlural coccyxes, Plural coccyges

  • A small triangular bone at the base of the spinal column in humans and some apes, formed of fused vestigial vertebrae.

    • ‘Many of my patients have pressure ulcers on the coccyx or sacrum.’
    • ‘From splintered bones in the coccyx, she was bedridden for nearly two years.’
    • ‘The sacrum itself represents 5 fused bones, and the coccyx another vestigial 2-3 or more - the remains of the ancestral tail.’
    • ‘For that matter an injury to the spine or the coccyx also qualifies as affecting the automatic nervous system.’
    • ‘The spinal column is composed of seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, the bony sacrum, and the coccyx.’


Late 16th century: via Latin from Greek kokkux ‘cuckoo’ (because the shape of the human bone resembles the cuckoo's bill).