an extreme, rapid series of emotions that leave everyone involved including the person who is experiencing the emotions confused, disoriented and/or confused
Becky went from calm to sobbing to gleeful to pissed to dispondent all in one day. This frustrated and confused her parents, friends and Becky herself. They experienced moodswing whiplash.
A Manhattan Moodswing begins when you are fucking a girl in the ass and you sense a sudden mood change for no apparent reason. You then lift a nearby cinder block over the girl's head and knock the bitch out. You then flip her over and start doing her hardcore in her limp vagina.
girl: LIEK OMG ITS 1D
girl: OMFG I HATE THEM ALL guy: *facepalm* stupid moodswinging teenage girls we all know this is stupid and i'm really not felling it anymore