Can either be:

1) When someone posts the exact same thing twice in a row.

2) When someone posts something then, rather than using the "edit" button, posts an elaboration or similar right after the 1st.

3) Simply two posts by the same member, regardless of reason, after each other.
person1: I am cool...
person1: I am cool...
person2: aaargh double post!

person1: how good is an 8800?
person1: wait I mean an 8800GTX?
person2: try using 'edit' next time.

person1: I am cool...
person1: I like sausages...
person2: idiot!
by AlexAssassin June 17, 2009
1. A double post is two posts in a row that can be made into one post, but the person decides to post it in two separate posts. The posts have to have a common element though, if not it is just rambling.

2. Double(meaning two) posting is two posts in a row, but this is not what Admins and Moderators are really referring to when they say “no double posting allowed on forums.”
1a. ADAM- I really hope school starts back up soon, I really miss everyone.
1b. ADAM- I just collected three new Pokemon cards to add to my deck.

2a. MAX- I hurt my foot yesterday.
2b. MAX- I think it might be broken or something.
by Tocaru February 8, 2006
Two posts in a row that may or may not have the same meanings.
Complete disregard for the edit button.
Bob: I like pizza.
Bob: I also like pie.
by Mike March 7, 2005
Two posts, in succession, in a forum topic created by the same person that say the exact same thing.
This is a doubble post:

yorkky: I like pie.
yorkky: I like pie.

This is not a doubble post:
yorkky: I like pie.
yorkky: I also like cake.
by Nitron_F117 April 27, 2004
When a post is the same as another post by the same member in the same topic.
Guy1: Hello, can you fix this error, when I login , it just says error, and it won't let me login
Guy2:Please read the news section.
Guy1: so can you fix this, because it won't let me login because of this error.
Guy2: please don't double post.
by Rensen May 13, 2006