used to denote a person who gets completely drunk. In the first place, it assumes that he or she starts climbing trees while being intoxicated, acting weird and doing things he/she won't remember the next day.
A person who can be easily called a party animal (has nothing to do with drugs though, only alcohol).
Made of russian "дереволаз", where
"дерево" - a tree
"лаз" - climber.
Literally translated as a treeclimber.
"he was such a derevolaz yesterday! I'll never forget this night"
"that was a real derevolaz party, with tons of beer and dozens of crazy people"