look up any word, like half chub:
 
1.
Having someone come along for a ride in order to use the carpool lane. Only for the purpose of getting to the destination faster, not companionship.
Yeah I had to get to school fast because I was late so I used John as seat meat.
by rockntubakid April 26, 2010
 
2.
The flesh that gets trapped in gaps and holes in seats and pokes out. Especially with fat people and garden chairs
Look at that land whale her seat meat looks like you could cut it off and fry chips in it.
by whalesharkz December 05, 2013