Giving Oral Sex to Male from Female or Receiving Oral Sex from Female to Male..(Female giving to Male) In other words getting some Dome or Head or Brain.
Man, last night I picked up this chick at the Bar and took her to my car and she gave me Head Jacks.
The other day my ol' lady gave me some Chilly Head Jacks!
One who thinks he/she is super great and attractive and must be idolized. Very selfish. Their head is so humongous that it cannot fit through a doorway. Comes on suddenly. Usually induced by alcohol. Includes a jumbo full teeth smile that is very phony. Lives a lifestyle which includes champagne wishes and caviar dreams on a beer budget. Always overshadows their mate. Is often seen as a family trait.
Can also be a verb: jackheadness
OMG look at that guy that thinks he is so great, he has his Jack Head on
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.