When someone is coughing all the time and won’t stop

cough cough is used to subtly imply that you know something that someone else doesn't. The person who it is "used on" will then begin to suspect something is suspicious with the phrase "cough cough" and will begin to wonder what it means. Mostly, "cough cough" is pronounced as a word, instead of being actually "coughed out".

Those special times when you can't say something, so you just, ya know, sort of cough...

Dying of corona.

Description of disgusting people in the wake of the Covid-19 Coronavirus pandemic, certain people with horrible etiquette in social distancing and/or individuals deliberately coughing or otherwise expelling breath wildly and inappropriately. (Similar to the insulting names, “jerk off” and “douchebag”)

a) When someone acts or says something that figuratively makes you sick.

b) When someone is just wrong in general, often due to being an unpleasant or actively ignorant person.

Is pronounced like the word "coffin"

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.