(archaic, principally nautical) In a state of collision or entanglement.
The ships’ lines and sails were all afoul.
1849, William F. Lynch, The Naval Officer, Chapter 2, in Graham’s Magazine, Volume 34, Number 3, March 1849,
The atmosphere was soon thick and stifling, and the crews were working their guns with the energy of desperation, when a severe concussion, followed by a harsh and grating sound, told that the ships were afoul.
(with of) In a state of entanglement or conflict (with).