The Collaborative International Dictionary
Lubber \Lub"ber\, n. [Cf. dial. Sw. lubber. See Looby, Lob.] A heavy, clumsy, or awkward fellow; a sturdy drone; a clown.
Lingering lubbers lose many a penny.
--Tusser.
Land lubber, a name given in contempt by sailors to a person who lives on land.
Lubber grasshopper (Zo["o]l.), a large, stout, clumsy grasshopper; esp., Brachystola magna, from the Rocky Mountain plains, and Romalea microptera, which is injurious to orange trees in Florida.
Lubber's hole (Naut.), a hole in the floor of the ``top,''
next the mast, through which sailors may go aloft without
going over the rim by the futtock shrouds. It is
considered by seamen as only fit to be used by lubbers.
--Totten.
Lubber's line, Lubber's point, or Lubber's mark, a line or point in the compass case indicating the head of the ship, and consequently the course which the ship is steering.
Wiktionary
n. (context nautical English) A hole through the platform surrounding the upper part of a ship's mast, through which one may climb to go aloft.
WordNet
n. hole in a platform on a mast through which a sailor can climb without going out on the shrouds
Usage examples of "lubber's hole".
He was so stiff that he went down through the lubber's hole, chuckling to himself as he did so -'Lord, what a fat-arse I have become.
Bonden was still peering down the lubber's hole, the way Stephen had always come before, the safe, direct, logical, but ignominious road.
Their only relief from boredom came when Graham, in the heat of declamation (Plutarch on Pyrrhus), stepped backwards into the lubber's hole, and when they were sent down for maps and an azimuth compass so that it might be determined which mountain on the skyline concealed Dodona and its speaking oak - 'Dodona, young gentlemen, which Homer describes as the hole of the Selli, who sleep upon the ground and do not wash their feet.
From immediately under the top Jack threaded Hanson up through the lubber's hole, himself taking the backward-leaning futtock-shrouds and dropping from the rail to join him.
But with more eyes fixed upon him than the approaching frigate, he could not take the easier passage of the lubber's hole.