Burglar alarm

from WordNet (r) 3.0 (2006)

burglar alarm
    n 1: a loud warning signal produced by a burglar alarm; "they
         could hear the burglar alarm a mile away"
    2: a warning device that is tripped off by the occurrence of a
       burglary

from The Collaborative International Dictionary of English v.0.48

Burglar \Bur"glar\, n. [OE. burg town, F. bourg, fr. LL. burgus
   (of German origin) + OF. lere thief, fr. L. latro. See
   {Borough}, and {Larceny}.] (Law)
   One guilty of the crime of burglary.
   [1913 Webster]

   {Burglar alarm}, a device for giving alarm if a door or
      window is opened from without.
      [1913 Webster]