Not tight; loose — describes something that is slack or not firmly fastened.
ズボンが緩くてベルトが必要だ。
The pants are loose so I need a belt.
ネジが緩いせいで機械がガタガタする。
The machine rattles because a screw is loose.
このバッグは口が緩いから中身が落ちないか心配だ。
I'm worried the bag's opening is loose and things might fall out.
Lenient or lax — not strict in enforcement or standards.
あの先生は宿題に対してかなり緩い。
That teacher is pretty lenient about homework.
セキュリティが緩いと情報漏えいの危険がある。
If security is lax, there is a risk of information leakage.
規則が緩い会社は自由度が高い反面、管理が行き届かないこともある。
Companies with lax rules offer more freedom but may lack proper management.
Gently sloping or curved — describes a mild incline or gentle curve.
この道は勾配が緩いので自転車でも登りやすい。
This road has a gentle slope, so it's easy to ride up by bike.
山道のカーブが緩いからスピードを出しやすい。
The mountain road has gentle curves, making it easy to pick up speed.
Slow or weak — indicating reduced force, intensity, or speed.
風が緩くなってきたので海が穏やかだ。
The wind has calmed down, so the sea is calm.
試合で相手の攻撃が緩く、すぐにコントロールできた。
The opponent's attack was weak, so we were able to control it quickly.
Soft; not firm — lacking stiffness or firmness (often for fabric, structure, or texture).
このセーターは編みが緩いので形が崩れやすい。
This sweater has a loose knit, so it easily loses its shape.
布団が緩くて寝返りするとずれてしまう。
The futon is loose, so it shifts when I turn over in my sleep.
Dialectal (Hokkaido/Tohoku): used in negative form to mean 'not easy' or 'not simple' (e.g., ゆるくない).
この仕事、ゆるくないよ。気を抜けない。
This job isn't easy. You can't let your guard down.