Learner's definition of VAIN
1 [also more vain; most vain] : too proud of your own appearance, abilities, achievements, etc. : conceited 2 : having no success : not producing a desired result
They made a vain [=unsuccessful] attempt to escape.
A vain effort to quell the public's fears only made matters worse.
Volunteers searched the area in the vain hope of finding clues.
: without success : without producing a good or desired result
We searched in vain for the missing earring. [=we searched for the missing earring but did not find it]
He tried in vain to get the baby to sleep.
Her suffering will not be in vain. [=something good will happen because of her suffering]
take someone's name in vain
: to use (a name, especially the name of God) in a way that does not show proper respect