When the back, specifically the lats, are worked out so hard that they, overtime, turn into solid steel. It is as if the man with the ripped back is wearing a cape, hence the term 'skin cape'.
'Dude, what is that on your back?', said the skinny man to the ripped fella on the lat-pulldown machine. 'Its my skin cape, its real, and its bulletproof.'
by jonnyclan January 26, 2006