(adj) When a person, group, or other collective makes a decision(s) or commit action(s) that present problems for them and/or others which would tend to make an unbiased third party observer believe the perpetrator(s) is(are) mentally unstable.
"Joann's tendency to throw up after she eats is very problemental."
"Stevo has been so problemental lately; his irrational behaviors are quite disconcerting."
"The NRA's defense of guns after the Sandy Hawk Massacre is very problemental."
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.