Source : Webster's Revised Unabridged Dictionary (1913)

Lighthouse \Light"house`\ (-hous`), n.; pl.{Lighthouses}
   (-houz`[e^]z).
   A tower or other building with a powerful light at top,
   erected at the entrance of a port, or at some important point
   on a coast, to serve as a guide to mariners at night; a
   pharos.