a·thwart·ships (?-thwôrt?sh?ps?) also a·thwart·ship (-sh?p?)adv. Across a ship from side to side. American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.athwartships (???w??t???ps) adv (Nautical Terms) nautical from one side to the other of a vessel at right angles to the keelCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014a?thwart?ships (???w?rt???ps) adv. from one side of a ship to the other. [1710?20] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.