1 : (also more vain; most vain) : too proud of your own appearance, abilities, achievements, etc. : CONCEITED
She is very vain about her appearance.
He is the vainest man I know.
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.
in vain
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
He took God’s name in vain.
(humorous) I thought I heard someone taking my name in vain. (=saying my name)
– vainly adverb
We tried vainly to get a taxi.
Volunteers vainly searched for clues.