solid
n.— «Yes, he agrees, they’re despised by the rest of the inmates, whom he refers to as “solids,” bank robbers and the like.…“A tattoo is an ID,” he explains. “It shows you’ve done time. It says, ‘I’m solid.’”» —“Just chatting with an ex-con” by Peter Duffy Chronicle Herald (Halifax, Nova Scotia) Feb. 22, 2007. (source: Double-Tongued Dictionary)