1.When you dating someone just to get over someone or just dating around until you're ready to get back on horse.
You Know Dave is Sally's place-holder, Until she's ready to walk down the aisle. Poor Dave
When someone is dating someone else just for them to be there, simply to be able to say "yeah I'm actually taken" even though they hate each other.
"I swear to God, Nick is just using Jen as a Place-Holder!"
"I'm bored....Lets go find us some place holders" -- guys
Friend 1 - "God i fucking hate Michelle!"
Friend 2 - "Aren't u dating her?"
Friend 1 - "Yeah"
Friend 2 - "Well here she comes"
Friend 1 - "Hey baby!"
The guy/girl that is dated or messed around with until the user can get the guy/girl that ditched them to come back.
Often the user was just a place-holder for said ex and didn't know it/can't get over him/her.
girl:Oh yeah I can't wait to hang out with you tomorrow <33!! love you baby
guy:*awesome this is love ^.^*
The following Evening:
girl:Yeah...I'm back with <insert douchebag that just ruined your fucking life> and I wasn't really in love with you.
guy:*Holy fucking shit I'm going to kill myself as soon as I finish thinking this.*
Perfect example of a Place-Holder...often suicide IS the result of being a Place-holder.
Other results are binge-drinking and death threats.