Tonitruous is an uncommon word that is used to describe a loud or thunderous sound. Some synonyms for tonitruous include resounding, thundering, deafening, booming, and thunderous. Resounding is used to describe a sound that echoes strongly or is very clear and distinct. Thundering and booming are both related to the sound of thunder and can be used to describe extremely loud noises. Deafening is another word used to describe a sound that is so loud it can cause temporary hearing loss. Finally, thunderous is similar to tonitruous and is used to describe any loud and rumbling noise, whether natural or man-made.