Thayer's Greek Lexicon

 1. a setting or placing under
  1) thing put under, substructure, foundation
2. that which has foundation, is firm
  1) that which has actual existence
2a1. a substance, real being
  2) the substantial quality, nature, of a person or thing
  3) the steadfastness of mind, firmness, courage, resolution
2c1. confidence, firm trust, assurance