The strength of the defense begins at the front line and flows backward.

Normally, these valves open to let blood flow through or out of your heart, and then shut to keep it from flowing backward.

For example, urine might flow backward from the bladder into the kidneys.

Lachesis had said time flowed backward here, which meant these people should be from the world's future, but now he wasn't so sure.

The equations remain true even when time flowed backward.

The layer of cloud was now flowing backward, into the fireball.

"Why don't you tell the Mississippi to flow backward?"

He jerked his attention upward and the object appeared to flow backward up into the dark sky.

The debris would flow backward, leaving the ship's hull unmarked.

The tide of progress, in other words, sometimes flows backward.