to thunder or roar: to give out a loud, rolling, resonant sound, whether God thundering from the heavens or the sea roaring
At its core this word imitates a sound: the deep, rolling boom of a thunderstorm. When God is the one who does it, he thunders from the sky; when the sea does it, it roars. The same booming, resonant noise is in view either way.
The word clusters in Israel's oldest storm poetry, and that is no accident. In the surrounding nations the storm-god's signature was his thunder-voice, and the poems of the Bible deliberately claim that very picture for the LORD: the sound of the storm is the sound of him speaking (קוֹל). When he thunders from heaven, the writers are announcing that the power every other people credited to their weather-god belongs to him alone.
It sits close to other Hebrew words for a loud, sustained sound, such as the roar of a lion or of God himself (שָׁאַג) and the surging roar of the sea (הָמָה). What sets this word apart is the specific image of thunder.
One twist is worth noticing. When the sea roars in the praise psalms, it is being summoned to celebrate, standing alongside the fields and the trees in worship. Older stories heard the roaring sea as a threat, the voice of chaos to be tamed; here that same roar has become an act of joy.