out of fashion or obsolete
bell bottom jeans and elevator shoes were considered old hat at one time, but now they're back in style.
Refered to when something has been brought up, or posted on forum multiple times.
"this is such an old hat, find something original"
someone that is a bit emo. could possibly be a lesbian, due to quirkiness. loves panic at the disco. has never read "where the wild things are", and plays bass for rockband.
That girl Maegan, she's old hat! Just look at her!
An little old woman in a HUGE old car wearing a big floppy hat, the hat is about all you can see behind the wheel of the gigantic car.
Be careful when traveling the Garden State Parkway down the shore, you're sure to run into an old hat or two!
A previously worn condom.
I couldn'y find a new one, so I used the old hat from last night.
An alteration of the term new shoes
, meaning to burp.
Paul: 'old hat!'