Be out of your tree
Definition 1 of 1
Pro Tip 1/3Connotation
Expresses strong disbelief or amazement at someone's actions or ideas. 
He's out of his tree for trying to skateboard off the roof!
Pro Tip 2/3Not Literal
Used figuratively; it doesn't mean someone is physically in a tree. 
She puts ketchup on everything, even ice cream – she's out of her tree!
Pro Tip 3/3Casual Use
Typically used in informal situations among friends or peers. 
You're out of your tree if you think that's the correct answer.