From Longman Dictionary of Contemporary Englishsomebody is all wetsomebody is all wetAmerican English informalWRONG/INCORRECT someone is completely wrong → wet
Examples from the Corpus
somebody is all wet• Yes, the point at which we conclude that your reasoning is all wet.• It is all wet and then he had like a side view of it.• I peer into the rain for a glimpse of Storskarfjell, but it is all wet misery to the south. 