Superlative form of straight: most straight.(adjective)
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Use "straightest" in a sentence
"And to him like a bird uncaged I flew in straightest line:"
"Of these 350 we have selected 50 which are the tallest and straightest, that is, 20 inches and over."
"I think the book that has stuck with me the longest is "Player Piano," even though I haven't read it in many years and it is, in many ways, the "straightest" of his books."