to become red in the face, for example when you are angry or embarrassed [= blush]:
Susan flushed deeply and looked away.
He flushed angrily.
Robyn felt her cheeks flush scarlet.
Mrs Cooper flushed with indignation.
if you flush a toilet, or if it flushes, you make water go through it to clean it:
toilet[intransitive and transitive]DHT
Why do children never remember to flush the loo?
She flushed the rest of her drink down the toilet.
to force water through a pipe in order to clean it
flush something through something
They flush clean water through the pipes once a day.
flush somebody/something ↔ outphrasal verb
to make someone leave a place where they are hiding:
The government is determined to flush out the terrorists.
to clean something by forcing water through it:
The heating system needs to be flushed out once a year.
Drinking water helps flush out toxins from the body.