Comparative form of hollow: more hollow(adjective)
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Use "hollower" in a sentence
"Given his eager participation in tomorrow's Tea Party seminar, his words ring hollower than ever."
"During fasting, since the body is not busy with gastric processes and since the body is literally emptier, hollower, I believe the nada practices can be even more effective."
"But if you're not into conspicuous consumption, get a wood call anywhere you can .. the bigger and hollower, the better."