IPA: /ˈkæv.ər.nəs.li/
KK: /ˈkævərnəsli/
In a way that resembles a large, hollow space, often producing a deep or echoing sound.
The singer's voice resonated cavernously in the empty hall.
Cavernously → It is formed from "cavern" (from Latin "caverna", meaning cave or hollow) and the suffix "-ously" (meaning in a manner of). The word "cavernously" describes something that is done in a manner resembling a cavern, often implying a deep, echoing quality.
Think of a 'cavern' being a large, hollow space, and when something is done 'in a manner of' that cavern, it has a deep, echoing quality.