n. The upper arm of an overweight person, referring to the size of the arm (which more closely resembles the thigh due to staggering amounts of arm fat). Most often spotted at buffets, rodeos, NASCAR events, state fairs, Wal-Mart stores, Jerry Springer's television program, and throughout the South. Very often seen in conjunction with thankles.
"Holy crap - that is the fattest arm I have ever seen. They're supposed to be biceps, not thighceps. Your arms look like pillowcases full of cottage cheese. Maybe put the fork down once in a while, mmmkay?"