An ailment characterized by a sore, stiff or otherwise uncomfortable feeling in or around the neck and attributable to extended, or perhaps simply incorrectly administered, oral sex. Usage is exactly like one would use "tennis elbow." The first word (head) defines the activity and the second word (neck) refers to the body part that is suffering as a result of performing the activity. Appears in both genders and can be associated with fellatio, cunnilingus or even analingus. It truly is an equal opportunity malady.
"Heck Bill, I'd really love to go down on you today, but I have a really severe case of head neck."