head restraint vs pillion

head restraint

• The headrest of a seat in a motor vehicle. 

pillion

• A similar second saddle on a motorcycle for a passenger. 

• The person riding in the pillion. 

• The cushion of a saddle. 

• A pad behind the saddle of a horse for a second rider. 

• Riding behind the driving rider, as when positioned on the rump of a mount. 

• To ride on a pillion. 

• To put a pillion on a horse.