deliberately short-term sexual relationship between two people. Longer than a one-night stand, not as serious-sounding as "affair", more frankly physical than the discreet or twee "dalliance", the word has the associations of a much-needed sexual relief from stress, worry or hangups. No deep personal involvement required, just the sex and a bit of attention.
Office gossip: Oh, by the way, I heard about your secretary's latest fling!
Minor boss: Whaurrgh (choking on his croissant) - How did you find out?
Office gossip: ... With one of the young trainees. Hey, just a minute (grinning with delight) ....
Minor boss: What? Look, I didn't say anything! Err ... which trainee? (under his breath: the double-dealing BITCH!)
By kofi