Simple past tense and past participle of clamp.(verb)
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Use "clamped" in a sentence
"His expression clamped into formidable austerity, then relaxed."
"The Lakers once again clamped down on the perimter shooters of the Spurs and limited Tim Duncan to a playoff-low nine points on"
"UPDATE 20071017 Andrew Linden apparently is listening to us, and only the megaprims over 256 m on a side are going to be removed or "clamped" down to 256 m, as he describes it."