"vacuous" in the adjective sense
1. mindless, vacuous
devoid of intelligence or thought
"a vacuous mind"
"a vacant expression"
2. empty, hollow, vacuous
devoid of significance or force
"empty promises"
"a hollow victory"
"vacuous comments"
3. vacuous
devoid of matter
"a vacuous space"
Source: WordNet® (An amazing lexical database of English)
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