mad ‧ ness /ˈmædnəs, ˈmædnɪs/ BrE AmE noun [uncountable]
1 . especially British English very stupid behaviour that could be dangerous or have a very bad effect
it is madness (for somebody) to do something
It would be madness to drive all that way on your own.
Cutting down the forest is sheer madness (=completely crazy) .
2 . serious mental illness SYN insanity :
His family has a history of madness.
3 . moment/fit of madness when someone does something without thinking clearly:
In a moment of madness, I agreed to have the party at my house.
⇨ there’s method in/to sb’s madness at ↑ method (3)