Re: *cough*
From the Urban Dictionary,
*cough*
Used on forums, chat, etc. to represent awkwardness, or break silence. Rarely used to actually represent coughing, unless someone is explaining how they have the flu or something.
-- A little more specific --
Cough:
1. Used mostly on a chat, or a forum, as a response to something awkward.
2. Used to tell others you have a cough or something.
*Any clash between real names in the example is entirely coincidental*
Example of Definition 1:
Jamie: Hey whats 1 + 1?
Jack: *cough* *cough*
Example of definition 2:
Jamie: Hey, hows it going?
Jack: I *cough* have a cough.