v. & n.
v. 1 intr. make a continuous deep resonant sound as of distant thunder. 2 intr. (foll. by along, by, past, etc.) (of a person or vehicle) move with a rumbling noise. 3 tr. (often foll. by out) utter or say with a rumbling sound. 4 tr. Brit. sl. find out about (esp. something illicit).
n. 1 a rumbling sound. 2 US sl. a street-fight between gangs. rumble seat US an uncovered folding seat in the rear of a motor car. rumbler n.
[ ME romble, prob. f. MDu. rommelen, rummelen (imit.) ]