sag in WordNet English dictionary

1. a shape that sags
   "there was a sag in the chair seat"
   sag  droop 
   

1. droop, sink, or settle from or as if from pressure or loss of tautness
   sag  droop  swag  flag 
   
2. cause to sag
   "The children sagged their bottoms down even more comfortably"
   sag  sag down