Verb. The act of giving a monologue before killing someone. Also, the act of giving a monologue before being killed. In both instances, this is used to dramatic effect in movies.
The name is taken from the actor Samuel L. Jackson who has made extensive use of this effect.
See Jules Winnfield in Pulp Fiction and Russell Franklin in Deep Blue Sea, where Samuel L. Jackson sam-jacks someone and himself is sam-jacked.
Also, the Boondock Saints movie contains several similar scenes where the brothers sam-jack criminals while reciting a Catholic prayer.