Pen, writing impliment. Used instead of the word "pen" in order to make it sound more technical and complicated, even though it's just a pen.
Darnell: Yo, let me see that inkpen so I can write this bitch a check.
Jane: Inkpen? You mean a PEN?
Darnell: Don't be stupit, gimme that inkpen. Yeah, PEN!
Jane: Why not just call it a pen?
Darnell: Keepin' it real. Bitch.
this is just a joke example