A b word meaning helpful is beneficial.
Another word for kindly beginning with 'b' is benevolent.
booing
boffo, bizarre
Blunt
That would be bisecting.
When the word air means to air out, then the word beginning with B is bare (like when someone bares their soul).
Could it be "bud"?
Dweeb is a 5 letter word. It means a person who is socially awkward.
bisect
BEDECK (TG says so)
bauble
A b-word is any of a group of words beginning with B which may be considered rude or vulgar.