When someone's cell phone goes off in a classroom and everyone in that area coughs to cover it up. Normally used by students at up-tight high schools.
Megan's phone started goin off in English so we all gave her a courtesy cough so that the teacher wouldn't hear it.
Something that you do when you need to fart in a public place, and you know it's gonna be a loud one.
My Courtesy cough covered the noise, but there was no way i could cover the smell =D
The cough, necessary or not, made by a bathroom stall dweller, alerting outsiders that the stall is in use.
With the stall lock broken, Brad felt the need to give a courtesy cough, just in case someone felt the need to intrude on his private poop area.
A cough added for "punctuation" during a long speech to prevent run-on sentences, or to prepare the speaker when s/he isn't sure of what to say next.
You know the speaker is bored when he makes one too many courtesy coughs.