Rural PA slang for " pills ". Any pain pills such as oxycontin, vicodin, percocet, and so on. Illps are also known as illpocet clearly refering to percocets.
Joe : " I could really use a stress releiver right now "
Bob: " Let's go get some illps, i'm feinin "
or as an verb....
Joe : " you look fucked up "
Bob : " yeah, i'm really illped out right now "