Thayer's Greek Lexicon

 1. empty, vain, devoid of truth
  1) of places, vessels, etc. which contain nothing
  2) of men
1b1. empty handed
1b2. without a gift
  3) metaph. destitute of spiritual wealth, of one who boasts of his
faith as a transcendent possession, yet is without the fruits
of faith
  4) metaph. of endeavours, labours, acts, which result in nothing,
vain, fruitless, without effect
1d1. vain of no purpose