This word is used when one sees a sexy yummerific picture of Patrick Stump (lead singer, guitarist Fall Out Boy), instead of screaming: "OH MY GOD PATRICK YOU SEXY!" 20 000 times, one simply says: "Ohemgee. Patrickgasm."
(Imagine there is a sexy picture of Patrick over there) Wow. What a sexy and yummerific picture. Patrickgasm.