|Origin:||folie, from fol; FOOL1|
fol‧ly plural follies
1 [uncountable and countable] formal
a very stupid thing to do, especially one that is likely to have serious results:
Somerville bitterly regretted his folly at becoming involved.
the follies of aristocratic society
an unusual building that was built in the past as a decoration, not to be used or lived in