fill up

fill up
fill up
1. to become full. •

The creek filled up after the heavy rain yesterday.

The rain barrel began to fill up during the storm.

2. to fill one's gas tank. •

I've got to stop and fill up. The gas tank is running low.

We will fill up at the next little town.

* * *
or[fill it up] or[fill her up] {v. phr.} To fill entirely. (Said by the driver of a car to a gas station attendant). * /When the attendant asked Andrew how much gas he wanted in the tank, Andrew replied, "Fill her up."/

Dictionary of American idioms. 2013.