1. A contorted knot in wood; a cross-grained protuberance; a nodule; a boss or projection
   - knurl 
2. A knot in wood; a protuberance
   - knag

Derived forms: knurs

• sulfur mustard
• sulfur oxide
• sulfur paintbrush
• sulfur-yellow
• sulfurette
• sulfuretted
• sulfuric
• sulfuric acid
• sulfurised
• sulfurized
• sulfurous
• sulfury
• Sulidae
• sulindac
• sulk
• sulkily
• sulkiness
• sulky
• sulla
• sullage
• sullen
• sullenly
• sullenness
• Sullivan
• sully