fill up phrasal verb ( see also ↑ fill )
1 . if a container or place fills up, or if you fill it up, it becomes full
fill up with
Her eyes filled up with tears.
fill something ↔ up
Shall I fill the car up (=with petrol) ?
2 . fill (yourself) up informal to eat so much food that you cannot eat any more
fill (yourself) up with/on
Don’t fill yourself up with cookies.
He filled up on pecan pie.
3 . fill somebody up informal food that fills you up makes you feel as though you have eaten a lot when you have only eaten a small amount