Off (one's) gourd phrase slang
If someone is off his or her gourd, he or she is crazy.
He must be off his gourd if he thinks jumping from the second floor is fun.
What a ridiculous idea! You must be off his gourd.
After listening to his crazy idea, I feel like he is off his gourd.
Stupid or crazy
If you're off your trolley, your ideas or behaviour are crazy or insane.
Suddenly become crazy or very angry or lose control
Totally insane; overflowing with emotion, especially rage or enthusiasm
This phrase is used to describe something very modern or updated or something that no longer looks like what it's used to.
It has been a long time since I left my high school, and now I have to admit that it's certainly not your father's high school anymore.