Wiktionary
adv. (context nautical English) across the vessel sideways, i.e. in a direction at right angles to the fore-and-aft line of the vessel.
Usage examples of "athwartships".
Drummond could see the oilskinned figures grouping around her triple-mounted torpedo tubes, the purposeful way they were even now turning athwartships.
At all times except when whales were alongside, this bench was securely lashed athwartships against the rear of the Try-works.
He went up the steel ladder, through a second armored hatch, turned right, right again, down the passageway, up the ladder where the light was showing, through the athwartships passageway.
They watched in silence as the sheers moved forward to the stump of the Franklin's mainmast, fitting to it a curious object made up of yet another spare topmast and a hand-mast, the two coupled athwartships by two lower caps and a double upper cap above the refashioned maintop.
The shop was on the port side of the fo'c'sle deck cross-passage which ran athwartships for'ard of the wardroom, curving aft round the trunking of 'B' turret.