A swoner is a guy who "Swoops in with a Boner" a Swoner. This guy is the guy at work, in your group of friends or acquaintances (all LDS single wards have one) who is the first person to introduce himself to the new girl. This goes beyond being friendly. The swoner introduces himself, flirts, offers help to the new girl if she needs it, all with the hopes of getting his foot in the door before any other guy.
"Did you meet the new girl?"
"I was going to but Craig was talking to her already."
"Man, he's such a swoner."