'Burglar alarm' definitions:

Definition of 'burglar alarm'

(from WordNet)
noun
A loud warning signal produced by a burglar alarm; "they could hear the burglar alarm a mile away"
noun
A warning device that is tripped off by the occurrence of a burglary

Definition of 'Burglar alarm'

From: GCIDE
  • 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]