The senan is a dance move which is simply having the index finger of the left hand over your lips whilst the right hands index finger wiggles in the air, there are many adaptations such as the double handed wiggle( simply wiggling both index fingers and not covering the mouth.)
The senan is normally done to dance or trance music and the finger is normally wiggled in time to the music, the technical term for this being beatfingerwiggleyness.
I'm going to senan all nightlong. Look at me mother I'm senaning. Look at all those senanors they're so cool.
Seaning or to Sean is to have read and remembered all the rules, laws or regulations and be able to quote them with ease. Seaning is very useful when there's a dispute on the rules and the term first originated while playing boardgames.
Person A - I'm pretty sure you can't do that.
Person B - Aaaah, stop Seaning!