(usually with up or out) To make spiffy (attractive, polished, or up-to-date)

To reward (a salesperson) with a spiff or bonus.

To attach a spiff or bonus to the selling of (a product)

Very good, excellent.

“We're having a picnic at the races — how spiffing!”

Smart or appealing in dress or appearance.

“I say, that outfit is simply spiffing.”