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
sacrum (a triangular bone) and coccyx (a beak shaped
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.
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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.
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