Gear part is a term used to describe the components of a gear system. The three crossword solutions for this term are COG (3 letters), LUG (3 letters), and TOOTH (5 letters). A COG is a wheel with teeth that interlock with other cogs to form a gear system. A LUG is a short metal bar that is used to connect two or more cogs together. Finally, a TOOTH is a pointed projection on a COG that allows it to interlock with other cogs.