Period after a break up where you're looking for a new babe.
Dude 1: Bro are you still with Jessica?
Dude 2: nah dude, she broke up with me last week, I'm in the lame duck period
When you have committed to plans with a girl that you are not romantically interested in and therefore feel like you are not able to pursue a romantic relationship with anyone else until that commitment is fulfilled.
Typically in reference to a homecoming or prom type event.
“Hey man are you gonna slide on Hannah?”
“Dude I can’t until after homecoming cause I told Jenna I would go with her and I don’t want to look like a douche”
“Dang man, you’re really in a romantic lame duck period”