Any sexual act in which ejaculation is achieved within seconds.
"I've been wanting to fuck him for months. I wouldn't have wasted my time if I'd known it was gonna be a bloody quick- fire round"
"Last night, I was so horny from browsing online porn, I had to wake the missus up for a quick-fire round"
"I only had a few minutes to knock one off the wrist before my mum came home. Bit of a quick-fire round"