If someone is snippiest, they are being short-tempered or easily annoyed.
Being snippiest is not a good thing. It can make people feel uncomfortable or upset.
Examples:
She was the snippiest person in the room.
He gets snippiest when he's hungry.
The snippiest cat in the house is always grumpy.
The snippiest dog I know barks at everyone!
The snippiest teacher in the school never smiles.
My sister gets snippiest when she's tired.