1. Not monotonic

Antonym: monotonic

• steel guitar
• steel industry
• steel mill
• steel oneself against
• steel oneself for
• steel plant
• steel plate
• steel production
• steel trap
• steel wool
• steel-plated
• steel-wool pad
• Steele
• steelhead
• steeliness
• steelmaker
• steelman
• steelworker
• steelworks
• steely
• steelyard
• Steen
• steenbok
• steep
• steep-sided