Simple past tense and past participle of tighten.(verb)
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Use "tightened" in a sentence
"Its strange how Britain tightened its laws and they had literally no gun kills. yah its okay to have the little pistol with the safety but you should just rent a rugger at the range and get your action there"
"His expression tightened as he turned and started running."
"She glanced toward the floor and her expression tightened unhappily."