Source : Webster's Revised Unabridged Dictionary (1913)

Quarantine \Quar"an*tine\, n. [F. quarantaine, OF. quaranteine,
   fr. F. quarante forty, L. quadraginta, akin to quattuor four,
   and E. four: cf. It. quarantina, quarentine. See {Four}, and
   cf. {Quadragesima}.]
   1. A space of forty days; -- used of Lent.

   2. Specifically, the term, originally of forty days, during
      which a ship arriving in port, and suspected of being
      infected a malignant contagious disease, is obliged to
      forbear all intercourse with the shore; hence, such
      restraint or inhibition of intercourse; also, the place
      where infected or prohibited vessels are stationed.

   Note: Quarantine is now applied also to any forced stoppage
         of travel or communication on account of malignant
         contagious disease, on land as well as by sea.

   3. (Eng. Law) The period of forty days during which the widow
      had the privilege of remaining in the mansion house of
      which her husband died seized.

   {Quarantine flag}, a yellow flag hoisted at the fore of a
      vessel or hung from a building, to give warning of an
      infectious disease; -- called also the {yellow jack}, and
      {yellow flag}.

Quarantine \Quar`an*tine"\, v. t. [imp. & p. p. {Quarantined};
   p. pr. & vb. n. {Quarantining}.]
   To compel to remain at a distance, or in a given place,
   without intercourse, when suspected of having contagious
   disease; to put under, or in, quarantine.

Source : WordNet®

quarantine
     n 1: enforced isolation of patients suffering from a contagious
          disease in order to prevent the spread of disease
     2: isolation to prevent the spread of infectious disease
     v : place into enforced isolation, as for medical reasons; "My
         dog was quarantined before he could live in England"