Mentally unstable; crazy
ETYM Latin insanus. Related to In- not, and Sane.
Afflicted with or characteristic of mental derangement.
1. Enthusiastic, keen
2. Insane, crazy
1. Lacking seriousness; groundless lightheartedness.
2. Harmless; innocent; inoffensive.
3. Weak in intellect; destitute of ordinary strength of mind; foolish.