to make the water or liquid in something flow away:
The swimming pool is drained and cleaned every winter.
drain something from something
Brad drained all the oil from the engine.
Can you drain the spaghetti, please (=pour away the water from the pan)?
b) [intransitive always + adverb/preposition]
if liquid drains away, it flows away
I watched the bath water drain away.
if something drains, the liquid that is in it or on it flows away and it becomes dry:
Open ditches drain very efficiently.
She washed up and left the dishes to drain.
well-drained/poorly-drained soil (=soil from which water flows away quickly or slowly)
This plant needs rich, well-drained soil.
to make someone feel very tired and without any energy:
make somebody tired[transitive]
Working with children all day really drains you.
to use too much of something, especially money, so that there is not enough left:
use too much[transitive]
Huge imports were draining the country's currency reserves.
used to say that someone's face becomes very pale, because they are frightened or shocked:
When the verdict was read out, all the colour drained from Zelda's cheeks.
to drink all the liquid in a glass, cup etc:
Hannah drained her mug in one gulp.
drain awayphrasal verb
I watched the light drain away.
anger/confidence/tension/hope etc drains away
Sally felt her anger drain away.
drain something ↔ offphrasal verb
After cooking the meat, drain off the excess fat.