a word used to replace fuck when faced with having to tell the truth about having sex with a person even though you did'nt, but you still want others to believe that you slept with that person. .. . so it is kind of used as a verbal substitute for "fuck".
alex - hey george i heard from james that you totally did it with ashley last friday ?
george - yea man I totally *cough* fcuked *cough* her . ehm... last friday ..yea
alex - yo .. you caught cold or something ?
george - yea man we did it outside in the pool ....*cough*