armĭ-sŏnus, a, um, adj. [arma-sono],
resounding with arms (poet.): numina Palladis armisonae, Verg. A. 3, 544: antrum, Claud. Rapt. Pros. 3, 67.
armisonus adj. arma + SON-, resounding with arms : Pallas, V. ...
An Elementary Latin Dictionary