I’m not being rude; this is an actual mudra.
Mudras are gestures used in yoga and Ayurveda, ways to harness the direction of prana (energy) in the body. This one is called Tattva mudra, and it invokes truth.
The truth is sometimes sharp and cutting. It is sometimes not what we think we want (though if you dig deep, it is). Sometimes we are more inclined to run than sit the moment an honest person opens their mouth.
Truth is kind of like flipping the bird to the ego, who will sacrifice happiness for the sake of stability.
Unlike flipping the bird, the direction of Tattva mudra — and the truth that this mudra aligns us to — points inward.