Birthday.
biblican
backtalk, backpack, ballpark
Banister, bachelor, brawnier, brainier...
A 4 letter word that begins with B is bend.
bend..........
Boost is a synonym for the word lift and starts with the letter B.
Blurb
baobab.
butter
bunting
Bet
The word bat starts with the latter b and it ends with the latter a and t