Interjection used in a situation that is slightly uncomfortable, often accompanied by a gesture where the lower arm is thrust out parallel to the ground with the hand open and fingers together with thumb on top.
The overly messy explosion of semen, sperm, man juice, etc. all over the face of a woman who has just given a guy head. A cock-gun blast generally gets in the hair, eyes, nose, mouth, and just about anywhere you can think of.
Some whore was lickin my giggle stick and she told me to tell her when. I timed it just right that she pulled away and got a full-on cock-gun blast.