There are a total of 18 11-letter words containing 'turn', and the number may vary in different dictionaries. You can specify the dictionary and order.

• downturning ₂₁
• nocturnally ₂₁
• overturning ₂₀
• returnables ₁₇
• saturnalian ₁₅
• saturnalias ₁₄
• saturninely ₁₇
• taciturnity ₁₈
• turnarounds ₁₆
• turnbuckles ₂₅
• turntablism ₂₀
• turntablist ₁₇
• turnvereins ₁₈
• woodturners ₁₇
• woodturning ₂₀
• overturners ₁₄
• saturninity ₁₄
• unreturning ₁₂

There are 18 11-letter words containing turn in the well-known word game dictionary, 9 in the Scrabble US (US/Canada/Thailand - TWL/NWL) dictionary, and 13 in the Scrabble UK (International - SOWPODS/CSW) dictionary, and 15 in the Words with Friends (WWF) dictionary.