Lunacy is a synonym of foolhardiness.
As nouns the difference between lunacy and foolhardiness
is that lunacy
is (of a person or group of people) the state of being mad, insanity while foolhardiness
is the quality of being foolhardy.
(of a person or group of people) The state of being mad, insanity
# a cyclical mental disease, apparently linked to the lunar phases
# insanity implying legal irresponsibility.
Something deeply misguided.
* (state of being mad) insanity
The quality of being foolhardy.