Simple past tense and past participle of underline.(verb)
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Use "underlined" in a sentence
"Also, when there is a radio or TV on, I write the voices on it in underlined, italicized text."
"The other facet that ought to be underlined is that Hesser has tremendous affection for Mexico and its people."
"In his latest speech to the Russian Parliament, President Boris Yeltsin underlined the necessity of broadening the political and social base of our reforms by the consolidation of various political movements."