noun

a loud, deep, resonant sound.

the deep boom of the bass drum

reverberation,resonance,resounding,thunder,thundering,roaring,echoing,re-echoing,blasting,crashing,drumming,thrumming,pounding,roar,rumble,bellow,bang,blast,blare,loud noise

verb

make a loud, deep, resonant sound.

thunder boomed in the sky

reverberate,resound,resonate,rumble,thunder,ring out,sound loudly,blare,echo,fill the air,crack,crash,roll,clap,explode,bang,blast