taru-adjective, adverb taking the 'to' particle
roaring; booming; reverberating
Literary onomatopoeic word describing a deep, resonant, and continuous loud sound, such as thunder, cannon fire, or a large crowd. Often used in the form 殷々たる or 殷々と.
雷鳴が殷々と響き渡った。
The thunder roared and echoed all around.
殷々たる大砲の音が戦場を包んだ。
The booming sound of cannons filled the battlefield.
Variant without iteration mark; less common but valid.
The exact derivation is uncertain; the kanji 殷 is used for its meaning of 'rumbling' or 'booming', and the reduplication creates an onomatopoeic literary expression.