Adonai \Ad`o*na"i\, n. [Heb. ad[=o]n[=a]i, lit., my lord.] A Hebrew name for God, usually translated in the Old Testament by the word ``Lord''. Note: The later Jews used its vowel points to fill out the tetragrammaton {Yhvh}, or {Ihvh}, ``the incommunicable name,'' and in reading substituted ``Adonai''.