rum ‧ bling /ˈrʌmblɪŋ/ BrE AmE noun
1 . rumblings [plural] remarks that show that people are starting to become annoyed, or that a difficult situation is developing:
rumblings of discontent
There have been rumblings about the need for better computers.
2 . [countable usually singular] a series of long low sounds:
We heard a rumbling behind us.