'Rumbling' definitions:

Definition of 'rumbling'

From: WordNet
adjective
Continuous full and low-pitched throbbing sound; "the rumbling rolling sound of thunder" [syn: grumbling, rumbling]
noun
A loud low dull continuous noise; "they heard the rumbling of thunder" [syn: rumble, rumbling, grumble, grumbling]

Definition of 'Rumbling'

From: GCIDE
  • Rumbling \Rum"bling\, a. & n. from Rumble, v. i. [1913 Webster]