I. ə-ˈthwȯrt, naut often -ˈthȯrt preposition
Date: 15th century
1. : across
2. : in opposition to
a procedure directly athwart the New England prejudices — R. G. Cole
II. adverb
Date: circa 1500
1. : across especially in an oblique direction
2. : in opposition to the right or expected course
and quite athwart goes all decorum — Shakespeare