#3794 ὀχύρωμα ochuroma {okh-oo'-ro-mah}

 from a remote derivative of G2192 (meaning to fortify, through the
    idea of holding safely); TDNT - 5:590,752; n n

—Greek Word Study (Transliteration-Pronunciation Etymology & Grammar)

 1) a castle, stronghold, fortress, fastness
 2) anything on which one relies
    2a) of the arguments and reasonings by which a disputant endeavours
        to fortify his opinion and defend it against his opponent

—Thayer's (New Testament Greek-English Lexicon)

—Strong's (Greek Dictionary of the New Testament)

—NAS Exhaustive Concordance of the Bible with Hebrew-Aramaic and Greek Dictionaries

 AV - strong hold 1; 1

—Exhaustive Concordance (KJV Translation Frequency & Location)