v. & n.
v. 1 intr. a (often foll. by at) (esp. of a dog) make a low guttural sound, usu. of anger. b murmur angrily. 2 intr. rumble. 3 tr. (often foll. by out) utter with a growl.
n. 1 a growling sound, esp. made by a dog. 2 an angry murmur; complaint. 3 a rumble. growlingly adv.
[ prob. imit. ]