What is "to batten down the hatches"

Hatch \Hatch\, n. [OE. hacche, AS. h[ae]c, cf. haca the bar of a door, D. hek gate, Sw. h["a]ck coop, rack, Dan. hekke manger, rack. Prob. akin to E. hook, and first used of something made of pieces fastened together. Cf. Heck, Hack a frame.]

1. A door with an opening over it; a half door, sometimes set with spikes on the upper edge.

   In at the window, or else o'er the hatch.
   --Shak.

2. A frame or weir in a river, for catching fish.

3. A flood gate; a sluice gate.
   --Ainsworth.

4. A bedstead. [Scot.]
   --Sir W. Scott.

5. An opening in the deck of a vessel or floor of a warehouse which serves as a passageway or hoistway; a hatchway; also; a cover or door, or one of the covers used in closing such an opening.

6. (Mining) An opening into, or in search of, a mine.

   Booby hatch, Buttery hatch, Companion hatch, etc. See under Booby, Buttery, etc.

   To batten down the hatches (Naut.), to lay tarpaulins over them, and secure them with battens.

   To be under hatches, to be confined below in a vessel; to be under arrest, or in slavery, distress, etc.