A product (result, accomplishment, service, technology, whatever) that is great, or better than GoodEnough, that completely fills the stated goal. It's the thing you know there must be there when you find and settle with something GoodEnough.

Sometimes (rather few then a lot) you stumble upon something TheBest, and you learn you were so close but decided not to spend more on searching something better.

See TheBestIsTheEnemyOfTheGood.