(n); A combination of the words - thigh, and arm; term used to describe a woman's/man's upper arm that is very fat - looking very much like a "thigh".
Often, the fat rolls out from underneath the person's shirt sleeve.

When you eat dirt for the first time and leave your family to build a shack in the woods

When the loose upper arm is pushed up against your rib cage making your arm look as wide as your thigh. More prevalent amongst women in posed profile pictures.