A fucking hour is a fraction of time shorter than an actual hour. You know its like when a dude thought that he was fucking for an hour but it was like ten minutes, thats a fucking hour.
"We went across town for some food, I swear it felt like a fucking hour but was really just 20 minutes"
Person 1: Hey mannn, what time is it?
Person 2: 10:00.
*silence*
Person 1: Dudeee, what time is it now?
Person 2: It's still 10:00.
Person 1: ITS BEEN 10:00 FOR FIVE FUCKING HOURS!