cavernously

From cavernous + -ly.

cavernously (comparative more cavernously, superlative most cavernously)

1. In a cavernous manner; like a cavern.
   • 1933, Robert Howard, Black Colossus:

     The lurid unearthly glow still hovered in the shadowy chamber, lighting ghostlily the dead face of Thugra Khotan, which seemed to grin mirthlessly and cavernously at them.

2. In a cavernous manner; sounding deep, hollow, or echoey.
   • 1899, Stephen Crane, Making an Orator:

     ...the mother of the boy was alarmed beyond measure at Jimmie's curious illness, which caused him to lie on the rug in front of the fire and groan cavernously.