a. 1. Marked with, or exhibiting, folly; void of understanding; weak in intellect; without judgment or discretion; silly; unwise. [ 1913 Webster ]
I am a very foolish fond old man. Shak. [ 1913 Webster ]
2. Such as a fool would do; proceeding from weakness of mind or silliness; exhibiting a want of judgment or discretion; as, a foolish act. [ 1913 Webster ]