Simple past tense and past participle of slack.(verb)
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Use "slacked" in a sentence
"Here, lime water will refer to calcium hydroxide which is also known as slacked lime"
"We lost some games, wasn't playing well, and overall, our defense kind of slacked off."
"But this is where you start to wonder whether everybody kind of slacked off a little bit when Jobs, a notorious tyrant and perfectionist, wasn't around to put the fear of God into them."