The Collaborative International Dictionary
Guess warp
Guess warp \Guess" warp"\ (Naut.) A rope or hawser by which a vessel is towed or warped along; -- so called because it is necessary to guess at the length to be carried in the boat making the attachment to a distant object.
Wiktionary
guess warp
n. (context nautical English) A rope or hawser by which a vessel is towed.