Mentally Unstable

(1) Either used for someone who's mentally unstable, or as (2) a word thrown around to be used for insulting, name calling, so on, so forth.

1. ) Person A, "My god... they're mentally fucking unstable! Who's do such a thing?"

2. ) Person B, "no lol hahahahahahaha my sister is mentally unstable ashshhshshsahahsh she so craaaizy ahahahahahahahahh"