Jeffies are opioid analgesic medication synthesized from opium-derived thebaine. In other words any form of opioid medication. Usually in the form of but not limited to; oxycodone or hydrocodone. Many name brands of "Jeffies" are; Oxycontin "The King Jeffi", or weaker forms of "Jeffies" sch as Loraltab or Percocet. Other forms of "Jeffies" are such forms of opioid such as methadone, codeine, morphine, and even on some cases heroin. The name "Jeffi" derives from the people who sell drugs like these. When buying such drugs you have to deal with low life's that aren't legally named "Jeffi" but just look like they should be. This is from things like being overweight and having bent up glasses and being over medicated on Jeffies at all times.
Hey man you wana celebrate and grab a couple jeffies and watch a movie?" or "Dude im so jeffied right now I don't know when I'm asleep or when I'm awake its crazy brah." or "Man I love Jeffies but I hate Jeffi.