When a woman gives you a blowjob, while she is sitting on the toilet.
Guy 1: "Dude, this chick gave me a Carmichael last night!"
Guy 2: "No way! She's a freak!"
When you receive a blowjob from someone, while they are seated on a toilet. AKA reverse blumpkin.
Guy 1: "Dude, I got out of the shower last night and my girl immediately gave me a carmichael."
Guy 2: "Woah man, you've got a freak!"