1.NounSomething or someone excellent, surpassingly wonderful, or cool.
"We had strawberry shortcake for breakfast on Saturday and the kids thought it was the bee’s knees.; I used to play in a band when I was younger. We had a few fans and we thought we were the bee’s knees."
2.NounUsed other than figuratively or idiomatically: see bee, -'s, knee. Corbiculae.