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sluggish; languid; listless; heavy (heart, legs, etc.); dull
bothersome; tiresome; pain-in-the-ass
暑さのせいで体がだるいので休憩したいです。
I've felt sluggish since morning and can't move.
朝から体が懈くて仕事に集中できませんでした。
I continue to feel sluggish from the cold.
足がだるいのは昨日の運動のせいだと思います。
I'm becoming sluggish from the heat today.