Vitarka Mudrā

 Teaching Gesture
    Sjoquist p. 33 Vitarka Mudrā or Vyākhyāna Mudrā
    ānwèi yìn 安慰印
    This gesture indicates teaching, intellectual argument, and debate. The thumb touching the index finger completes a circle of understanding, while the other fingers remain outstretched. (When Americans make this sign, they usually mean “okay.”)
    Some important variants occur: if the thumb touches the middle finger, the gesture can mean compassion (so it is a gesture frequently seen in representations of Guānyīn); if it touches the ring finger, it can mean good fortune.

Source

anthro.ucsd.edu