1. Female to male or male to male oral copulation that is not only unsatisfying, but usually painful and never results in the recipient's ejaculation.
2. Felatio provided by someone unattractive, smelly, or otherwise undesirable to the receiver.
Hank tried to smile and moan appreciatively, but the scraping of Heather's teeth along his shaft and the death-grip she had on his balls resulted in the worst hellatio ever.