Source : Webster's Revised Unabridged Dictionary (1913)

Orlop \Or"lop\, n. [D. overloop the upper deck, lit., a running
   over or overflowing, fr. overloopen to run over. See {Over},
   and {Leap}, and cf. {Overloop}.] (Naut.)
   The lowest deck of a vessel, esp. of a ship of war,
   consisting of a platform laid over the beams in the hold, on
   which the cables are coiled.

Source : WordNet®

orlop
     n : the fourth or lowest deck [syn: {orlop deck}, {fourth deck}]