WordNet (r) 3.0 (2006):

signal light
    n 1: a fire set as a signal [syn: signal fire, signal light]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "signal light":
   Very flare, balefire, beacon fire, beacons, flare, flare-up, fusee,
   lighthouse, lightship, magnesium flare, occulting light, pharos,
   rocket, signal beacon, signal flare, signal lamp, signal rocket,
   skyrocket, watch fire