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Definition 2024

calvity ‎(plural calvities)

(uncountable) Baldness.
An area of skin that has become bald.
- 1972, Patrick O'Brian, Post Captain,
  He wore his own hair – what there was left of it: short tight curls round a shining calvity, though he was in his thirties, no more – and he looked like one of the fatter, more jovial Roman emperors […].

(baldness): The synonymous form calvities is more common. Though one appears to be the other's plural, in fact both forms are uncountable.