The Collaborative International Dictionary of English v.0.48:

Quinsy \Quin"sy\, n. [Contr. fr. squinancy, F. esquinancie, L.
   cynanche a sort of sore throat, Gr. ? sore throat, dog
   quinsy, fr. ? dog + ? to choke; cf. also L. synanche sore
   throat, Gr. ?. Cf. Hound, Anger, and Cynanche.] (Med.)
   An inflammation of the throat, or parts adjacent, especially
   of the fauces or tonsils, attended by considerable swelling,
   painful and impeded deglutition, and accompanied by
   inflammatory fever. It sometimes creates danger of
   suffocation; -- called also squinancy, and squinzey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quinsy
    n 1: a painful pus filled inflammation of the tonsils and
         surrounding tissues; usually a complication of tonsillitis
         [syn: quinsy, peritonsillar abscess]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "quinsy":
   Asiatic flu, Hong Kong flu, acute bronchitis, adenoiditis,
   aluminosis, amygdalitis, anthracosilicosis, anthracosis,
   asbestosis, asthma, atypical pneumonia, bituminosis, black lung,
   bronchial pneumonia, bronchiectasis, bronchiolitis, bronchitis,
   bronchopneumonia, catarrh, chalicosis, chronic bronchitis, cold,
   collapsed lung, common cold, coniosis, coryza, croup,
   croupous pneumonia, double pneumonia, dry pleurisy, emphysema,
   empyema, epidemic pleurodynia, fibrinous pneumonia, flu, grippe,
   hay fever, influenza, la grippe, laryngitis, lipoid pneumonia,
   lobar pneumonia, lung cancer, lung fever, pharyngitis, pleurisy,
   pleuritis, pneumococcal pneumonia, pneumoconiosis, pneumonia,
   pneumonic fever, pneumothorax, rheum, siderosis, silicosis,
   sore throat, swine flu, the sniffles, the snuffles, tonsilitis,
   virus pneumonia, wet pleurisy, whooping cough