There are a total of 19 11-letter words containing 'mouth', and the number may vary in different dictionaries. You can specify the dictionary and order.

• badmouthing ₂₄
• bonnetmouth ₂₂
• cottonmouth ₂₁
• foulmouthed ₂₃
• fullmouthed ₂₄
• hardmouthed ₂₁
• largemouths ₂₀
• loudmouthed ₂₁
• motormouths ₂₀
• mouthpieces ₂₃
• mouthwashes ₂₂
• openmouthed ₂₂
• pottymouths ₂₂
• smallmouths ₂₂
• widemouthed ₂₂
• poormouthed ₁₉
• flutemouths ₁₉
• smartmouths ₁₈
• snakemouths ₂₀

There are 19 11-letter words containing mouth in the well-known word game dictionary, 14 in the Scrabble US (US/Canada/Thailand - TWL/NWL) dictionary, and 18 in the Scrabble UK (International - SOWPODS/CSW) dictionary, and 15 in the Words with Friends (WWF) dictionary.