vain

Concise Oxford English Dictionary © 2008 Oxford University Press:
vain/veɪn/

▶adjective

• 1 having or showing an excessively high opinion of one's appearance or abilities.

• 2 producing no result; useless.

  ■ having no likelihood of fulfilment: a vain boast.

– phrases
in vain without success.
take someone's name in vain use someone's name in a way that shows a lack of respect.

– derivatives
vainly adverb.

– origin ME: via OFr. from L. vanus ‘empty, without substance’.