1.) The incident in which you make your presence known in prison in order to demonstrate that you are not one to be effed with. Best if done the day of or shortly after your arrival in prison.
2.) An incident in life in which one "goes for broke" in order to establish authority or street cred with others such as new co-workers, classmates or roommates.
The most poignant example, from which the term derives its name, is shanking a fellow prisoner in the neck while in the chowline after said prisoner cuts in front of you.
Sample sentence: "When Larry put his fist through the copy machine glass the first day of work then licked the blood off his fist with a smile, his prison chowline incident demonstrated to everyone at Intellefont IT Services that this guy was hardcore."