From The Collaborative International Dictionary of English v.0.44 [gcide]:
lightship \light"ship'\, Light-ship \Light"-ship'\(l[imac]t"sh[i^]p'), noun (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]
From WordNet (r) 2.0 [wn]:
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