'To be under hatches' definitions:

Definition of 'To be under hatches'

From: GCIDE

Hatch \Hatch\, n. [OE. hacche, AS. h[ae]c, cf. haca the bar of a door, D. hek gate, Sw. h[aum]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. [1913 Webster]
In at the window, or else o'er the hatch. --Shak. [1913 Webster]
2. A frame or weir in a river, for catching fish. [1913 Webster]
3. A flood gate; a sluice gate. --Ainsworth. [1913 Webster]
4. A bedstead. [Scot.] --Sir W. Scott. [1913 Webster]
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. [1913 Webster]
6. (Mining) An opening into, or in search of, a mine. [1913 Webster]
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. [1913 Webster]