Dream symbols and meanings from Bs to Bz are described here.

Bug or tiny insects : These creatures in dreams are often associated with irritation and frustrations.

Bullock cart : If it is associated as a vehicle, it denotes being relatively primitive.  Vehicles symbolise body or vehicle of expression.

Butterfly in a dream is a symbol of transformation or metamorphosis, as in a caterpillar becoming a  butterfly.

Buttock, backside, bum : Less obvious side of something. Unconscious aspects of oneself.