Definition of "unflood"

[…] Beatrice is now really letting the salt water flow freely, although her best effort is in Woodlawn two days later when it looks as if we will have to send for a siphon to unflood the premises.

a. 1946, Damon Runyon, Blonde Mink

And still I was diddling with the engine, fifteen, twenty, thirty, sixty pulls of the starting cord, fiddling with the choke, halfway, full choke, close choke, and flooding it, and waiting for it to unflood.

2013, George Szanto, Bog Tender: Coming Home to Nature and Memory, page 191