When a group of girls hound in on (and often scare) one guy to flirt with. symptoms may include girls acting like swarms; swarming from one guy to another at the same time. The exact reason for this gang-flirting tequnique is not known, but it seems the girls intend for something to eventually happen between them and the guy. (which it never does.)
It is quite an interesting phenomonen to watch. And tape. And play at their 21st birthday to embarass them. Unless they are 21.
And that would be sad.