Simple past tense and past participle of hollow.(verb)
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Use "hollowed" in a sentence
"But when Mr. Obama delivered his stunningly eloquent and inspiring address at midday on Jan. 20, he provided a powerful hint of what "bipartisan," a term hollowed out by habitual and insincere misuse, means to him now."
"Lumps of burning coal were also placed in hollowed gourds on doorsteps, to welcome deceased loved ones."
"They are arboreal and nocturnal, sleeping by day in hollowed out trees, tree crevices or branches."