Definition of "croup"

croup¹

/kɹuːp/

noun
plural croups
1. The top of the rump of a horse or other quadruped.
  Quotations
  So light to the croup the fair lady he swung, / So light to the saddle before her he sprung.
  1808 February 22, Walter Scott, “(please specify the introduction or canto number, or chapter name)”, in Marmion; a Tale of Flodden Field, Edinburgh: […] J[ames] Ballantyne and Co. for Archibald Constable and Company, […]; London: William Miller, and John Murray
  The guib [a kind of antelope] is of the mean dimensions, or four feet and a half in total length, and two and a half high at the shoulders, but rather higher at the croup.
  1835, Charles Frederick Partington, The British cyclopædia of natural history

croup²

/kɹuːp/

verb
third-person singular simple present croups, present participle crouping, simple past and past participle crouped
1. (obsolete outside dialects) To croak, make a hoarse noise.
noun
uncountable
1. (pathology) An infectious illness of the larynx, especially in young children, causing respiratory difficulty.