The word(s) "curve" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Pickthal translation.

(1) Wherein thou seest neither curve nor ruggedness.

(سورة طه, Taa-Haa, Chapter #20, Verse #107)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)

(2) And make mention (O Muhammad) of the brother of A'ad when he warned his folk among the wind-curved sandhills - and verily warners came and went before and after him - saying: Serve none but Allah. Lo! I fear for you the doom of a tremendous Day.

(سورة الأحقاف, Al-Ahqaf, Chapter #46, Verse #21)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)