1
general::
Phrase(s): all wet
1. Lit. completely wet. • I fell in and got all wet. 2. Fig. mistaken; wrongheaded; on the wrong track. • That’s not the correct answer, John. You’re all wet. • If you think that prices will come down, you’re all wet.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Completely wrong, mistaken, as in If you think you can beat the system and win at roulette, you're all wet. The original allusion in this expression is unclear, that is, how moisture or dampness is related to wrongness. [Slang; first half of 1900s]
American Heritage Idioms