An embarrassing and mythological maneuver one claims to had performed during and altercation in which he/she/questioning had unquestionably lost but cannot accept the loss and thus claims to had performed on the true victor in a pathetic display of denial .
"Remember that time I put buddy guy friend there in thee ole Scottish Arm Bar?"
A arm barn is the southern term for a circle jerk. Where a group of good ole boys get together to jerk each other off in a circle. An arm barn tends to be more rough than a circle jerk on account of all participants having blue collar jobs, thus leading to hands that know a hard day's work.
After working a hard day down at the mill, Brady was looking forward to getting together with the boys for a good old arm barn later.