A spare part is a replacement part used to repair or replace a broken, damaged, or worn out part of a machine. The term 'spare part' can refer to four different crossword solutions: TIRE (4 letters), RIB (3 letters), PIN (3 letters), and RIM (3 letters). TIRE is a circular piece of rubber that is attached to the wheel of a vehicle, while RIB is a long, thin strip of material that provides support and strength. PIN is a small metal rod with a pointed end, and RIM is the outer edge of a wheel. Finally, onepin is a type of PIN that has only one end.