Simple past tense and past participle of smoothen.(verb)
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Use "smoothened" in a sentence
"LRC cited that such is the case in Siocon town in Zamboanga del Sur where the NCIP office allegedly "smoothened" the FPIC process by "acquiring the consent with pseudo representatives from the Subanen tribe" despite the opposition of legitimate timuays led by Timuay Jose Anoy, owner of the Certificate of Ancestral Domain Title."
"Jugs have most often thin walls and their exterior surface is either simply smoothened or applied with an off-white slip (Figure 2)."
"Mr. Kothari said the decision to retire was taken earlier, but he waited for the merger between Merrill Lynch and Bank of America to be smoothened out before making a public announcement."