1. The part of the back between the lowest pair of ribs 
of the thorax (chest) and the top of the pelvis. The  
pelvis is a massive bone made of hip bones on each  
side and the front, while the back part is made of the 
bone). When loin is used in this sense, it is often used 
in reference to humans and non-human animals with 
four legs. This is why certain cuts of meat contain the 
word “loin” such as “sirloin” and “tenderloin” which both 
come from the rear back part of the animal.
 
2. The upper and lower regions of the belly and the region around the hips. 
3. The lowest part of the belly that is below the belly button and between the groin (where 
the belly joins the thighs). 
Loin most often refers to the first definition, mentioned above. Lumbar is an adjective that  
is commonly used to describe the area of the loin. Loin is also known as lumbus. The 
plural of loin is lumbi. 
Loin comes from the Middle English word "loyne" meaning "flank." Flank means the same 
thing as loin.