An explosion that starts with a B could be:
Boom, Bang, Blast.
Blast, boom, bang, bomb
I disagree with the above answer. "Blast" is a verb, not a noun. "Boom" and "bang" are both interjections, which express a noise or touch. "Bomb" is the only word that is a real explosion from up above. "Bomb" can be either a verb or a noun. Bomb the entire country! (In this sentence "bomb" is a verb.) The bomb exploded and blew up thousands. (In this sentence "bomb" was used as a noun.)
A bomb is a device. The explosion is a blast, usually accompanied by a bang or a boom. The bomb blast destroyed the surrounding houses... is a description of the explosion of a bomb. There was a loud boom as the bomb exploded... is also a description of the explosion of a bomb. The bomb exploded with a loud bang... is again another description of the explosion of a bomb.
blast
blast or burst
Bear starts with the letter B
The chicken that starts with B is bantam.
Belgium is a country that starts with B.
POOP YAY!!!!! -POOP MAN
a BMW starts with the letter b!!
A bumper sticker is sticky. It starts with the letter b.
Baclofen is a muscle relaxer that starts with the letter B
The word 'boom' can be used as a word for explosion that starts with a b.
Boost is a synonym for the word lift and starts with the letter B.
No country that borders Libya starts with the letter B.
A ballot is something that starts with b and is used to vote.