af-frĕmo — Lewis & Short
af-frĕmo (better adf-), ĕre, 3, v. n.,
I to roar, rage, growl, or murmur at (only in post-Aug. poets):
adfremit his (Mars),Val. Fl. 1, 528:
Boreas stridentibus adfremit alis,Sil. 14, 124.