Handwave

 HANDWAVE 1. v. To gloss over a complex point; to distract a listener;
       to support a (possibly actually valid) point with blatantly faulty
       logic. 2. n. The act of handwaving. "Boy, what a handwave!"
       The use of this word is often accompanied by gestures: both hands up,
       palms forward, swinging the hands in a vertical plane pivoting at the
       elbows and/or shoulders (depending on the magnitude of the handwave);
       alternatively, holding the forearms still while rotating the hands at
       the wrist to make them flutter. In context, the gestures alone can
       suffice as a remark.