What is the meaning of Vain?

Overly proud of oneself, especially concerning appearance; having a high opinion of one's own accomplishments with slight reason.

Having no real substance, value, or importance; empty; void; worthless; unsatisfying.

Effecting no purpose; pointless, futile.

Showy; ostentatious.

To frustrate. (The addition of quotations indicative of this usage is being sought:)

wine

only, merely, exclusively, solely, just

ever (when used with an interrogative pronoun)

An emphatic word used with the negative verb and -kö.

go ahead, be my guest ; definitely

useless, ineffective, fruitless

vain, shallow

vain

Source: wiktionary.org