cavernous

adjectives

being or suggesting a cavern
"vast cavernous chambers hollowed out of limestone"
is derived from
is similar to
not solid; having a space or gap or cavity
"a hollow wall"; "a hollow tree"; "hollow cheeks"; "his face became gaunter and more hollow with each year"
filled with vascular sinuses and capable of becoming distended and rigid as the result of being filled with blood
"erectile tissue"; "the penis is an erectile organ"