B
amoebas
cabinetcaboosedebtorsrebuiltonboardmobsterreboundsubsidywebsitetabletssubwayslobsterreboundrebateslibraryrabbitsdebrieffibbingembraceembargolabeledorbitedrebirth
abbigal
BagwormBantengBasenjiBettongBighornBitternBlesbokBuffaloBulldogBuntingBustardBuzzard
bursa
bunting
bathtub, brewpub
Some seven letter words starting with B are:bathtubdisturbperturbproverbrhubarbsuccumbtaxicabwashtub
cobbler
There is no 7-letter word using those letters, but there are two 6-letter options:confabforbad
Barter