The superlative form of the adjective 'swish', meaning the most stylish or elegant.
This word makes people think of fancy clothes, expensive things, and looking very good.
Examples:
She wore the swishest dress at the party.
That is the swishest car I've ever seen.
The swishest house on the block belongs to the mayor.
He has the swishest hat in the whole town.
The swishest restaurant in the city has gold plates.
The swishest cat in the world wears a tiny crown.