What does "loony" mean as a noun?

Native speaker’s answer
Rebecca
As a noun, a "loony" is a person who is crazy or silly! It can be used if someone acts or does something silly. However! It can also be a derogatory term for someone who is mentally ill, so be careful in what context you use it in. Ex: She went on the scary rollercoaster ten times. She's a loony. Ex: You're not a loony, George. What you did was reasonable. Ex: That's rude of you to call him a looney.