When the right palm is placed over the back of left palm, both palm being in Ardhachandra hasta.

Lets take a look at the viniyoga shloka

etasya viniyogastu sammatau matsyadarshane

It says that this gesture is used to denote a Fish. The Matsya Avatara of Lord Vishnu is also denoted by this gesture.

Related posts:

1. Kapota Hand Gesture (Mudra)
2. Samputa Hand Gesture (Mudra)
3. Mushthi Hand Gesture (Mudra)
4. Pushpaputa Hand Gesture (Mudra)

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