στερέωμα something established, i.e. (abstractly) confirmation (stability)Derivation: from G4732;KJV Usage: stedfastness. G4732
Thayer:1) that which has been made firm 1a) the firmament, the arch of the sky, which in early times was thought to be solid 1a1) a fortified place 1b) that which furnishes a foundation 1b1) on which a thing rests firmly, support 1c) firmness, steadfastness 1c1) metaph. in a military sense: solid front
στερέωμα stereōma ster-eh'-o-mah From G4732; something established, that is, (abstractly) confirmation (stability)KJV Usage: stedfastness.