Post Script 

An informal or personal addition at the end of a letter or note written to a friend, acquaintance, or enemy.

Could also apply to a notation added to the end of scripting or coding in terms of a computer language or semantics.

Common known acronym is P.S.

(contents of note blah blah blah)
Sincerely,
(name here)

P.S. (post script) I had a great time at dinner last night!

Post Script by k0nflict June 8, 2009

Postscriptionist

An advocate or creator of new vocabulary that has substantial, unique, and relevant meaning to a particular language or culture that has yet to be accepted as part of formal grammar.

Me: I definitely just roffled!
You: What do you mean by roffled?
Me: Roffled is the past tense of the acronym ROFL.
You: You are such a postscriptionist, but I agree that makes perfect sense!

Postscriptionist by ShoKill December 18, 2009