The abrupt turning of the head/face to the left or right with an utter look of disgust. May also be accompanied with "the hand."
That fool's nasty ass breath was all up in my face so I straight up had to give him sideface!
The random turning of the face away from another person in order to strike up conversation.
May be followed with flailing fingers in the shape of a mouth on the side of ones face.
Mctigue looked at me, the silence was so awkward i had to restrain myself from throwing up a sideface.