rumbly

It still rained very hard, but the wind did not howl so loudly, and the lightning was not so scary, nor the thunder so rumbly.

Buster Bear began to chuckle and then to laugh, and his laugh was deep and grumbly rumbly like his voice.

"I'm going fishing," said he in his deep grumbly-rumbly voice to no one in particular.

"I'm much obliged for the fine breakfast you have given me," said Buster in his deepest, most grumbly-rumbly voice.

Buster growled a deep, grumbly, rumbly growl and started up after him.