lightship \light"ship`\, Light-ship
\Light"-ship`\(l[imac]t"sh[i^]p`), n. (Naut.)
A vessel equipped like a lighthouse, carrying at the masthead
a brilliant light, and moored off a shoal or place of
dangerous navigation where a permanent lighthouse would be
impracticable, to serve as a guide for mariners; as, the
Ambrose lightship off New York was rammed and damaged in 1950
by the Santa Monica.
[1913 Webster + WordNet 1.5]