a violent shaking, and the roar or rattling such shaking makes: an earthquake, a rumbling commotion, or a body's trembling
At its core this word names a violent shaking, together with the roar or clatter that such shaking makes. Its plainest use is an earthquake: the ground heaving, mountains splitting, a whole land trembling. It is the word for the great quake in King Uzziah's day that people still remembered generations later.
From that base it stretches in two directions. It reaches outward to any loud, ground-shaking commotion: the rumble of war chariots, the rattle of a spear, the thunder of an advancing army, the din of battle. And it reaches inward to a person's own trembling, the shaking of a body gripped by fear. The same word can therefore be an earthquake, a stampede, or a shudder, because one force is heard in all three: something so powerful that it makes the world shake and roar. The matching verb רָעַשׁ names the act of shaking; this noun names the shaking as a thing.
The word also belongs to the language of God's approach. When the LORD passes by, the mountains quake; when his glory rises, a great rumbling is heard. Here the shaking is not merely a disaster but the mark of an overwhelming presence.