cavernously

adverb2

1. •
   In a cavernous manner; like a cavern.

   • 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. — 1933
2. •
   In a cavernous manner; sounding deep, hollow, or echoey.

   • ...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. — 1899