birthday Meaning, Definition & Usage

  1. noun an anniversary of the day on which a person was born (or the celebration of it)
  2. noun the date on which a person was born
    natal day.

WordNet

Birth"day` noun
Definitions
  1. The day in which any person is born; day of origin or commencement.
    Those barbarous ages past, succeeded next The birthday of invention. Cowper.
  2. The day of the month in which a person was born, in whatever succeeding year it may recur; the anniversary of one's birth.
    This is my birthday; as this very day Was Cassius born. Shak.
Birth"day` adjective
Definitions
  1. Of or pertaining to the day of birth, or its anniversary; as, birthday gifts or festivities.

Webster 1913