Flexception is when one "flexes" appearing or acting bigger than he/she really is, whether it would be financially, physically or mentally. For example, taking a selfie or picture next to a vehicle or property that is not yours. A "Flexception" is doing this (flexing) under certain circumstances such as being on vacation or somewhere at sometime no one can call you out on your bullshit. Example, a vacation in Vegas where you stayed at the holiday inn but posted pics of you checking into the Bellagio.
I really didn't want to take a selfie at the jewelry store with all this jewelry on, but I made a Flexception.
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.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"