Definition of bee noun from the Oxford Advanced Learner's Dictionary

bee

noun
biː
 
; biː
 
 
1 a black and yellow flying insect that can sting.Bees live in large groups and make honey (= a sweet sticky substance that is good to eat)a swarm of beesa bee stingBees were buzzing in the clover. see also beehive, beeswax, bumblebee, queen bee2 (North American English) a meeting in a group where people combine work, competition and pleasurea sewing bee see also spelling bee
Idioms

the bee's knees

(informal) an excellent person or thingShe thinks she's the bee's knees (= she has a very high opinion of herself).

have a bee in your bonnet (about something)

(informal) to think or talk about something all the time and to think that it is very importantOur teacher has a bee in his bonnet about punctuation.
more at the birds and the bees at bird, busy as a bee at busy adjective