penichillin' Share definition Flag A euphoric state of one's body and mind in total relaxation due to the use of antibiotic drugs. The doctor said I had a parasite and thanks to the meds they gave me, I'm just penichillin'. penichillin' by Johnny Shortwicks January 1, 2012 0 0 Get merch Get the penichillin' mug. Buy Now — $32.95 See more merch