A girl places a lemon on a guy's penis and proceeds to give him a hand job using that lemon. Then, the girl takes the lemon off and gives the guy a blow job. However, the blow job is exceedingly unsatisfying for the girl because the lemon has caused the penis to become very sour and acidic.
Natalie gave me a lemon job last night. It felt great except she kept having to stop every two minutes because she claimed my dick was too sour.