The Collaborative International Dictionary of English v.0.48:

Lazar \La"zar\, n. [OF. lazare, fr. Lazarus the beggar. Luke
   xvi. 20.]
   A person infected with a filthy or pestilential disease; a
   leper. --Chaucer.
   [1913 Webster]

         Like loathsome lazars, by the hedges lay. --Spenser.
   [1913 Webster]

   Lazar house a lazaretto; also, a hospital for quarantine.
      [1913 Webster] Lazaret

WordNet (r) 3.0 (2006):

lazar house
    n 1: hospital for persons with infectious diseases (especially
         leprosy) [syn: lazaretto, lazaret, lazarette, lazar
         house, pesthouse]