from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Lord. Used in Judaism as a spoken substitute for the ineffable name of God.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- proper n. YHWH, the ineffable name of God, is read as Adonai ("My Lord") or as Elohim. The word Adonai is normally used only in prayer, else the speaker risks taking the Lord’s name in vain. In normal speech, the word HaShem ("The Name") is used instead.
from the GNU version of the Collaborative International Dictionary of English
- n. A Hebrew name for God, usually translated in the Old Testament by the word “Lord”.
from The Century Dictionary and Cyclopedia
- n. A Hebrew name of God, reverentially used in reading as a substitute for the “ineffable name” JHVH, that is, Jehovah. See Adonist and Jehovah.
 All that can be remarked on this is, that the Jews substituted the term Adonai (#D+N+aJ+) for the name Jehovah, as often as the latter occurred in the sacred text.
The term Adonai is used in the Shema prayer that is the ultimate prayer for Jews.
"Adonai" is the Hebrew for "Lord" (subsituted in for YHWH when reading aloud from the Torah).
Greenberg explains that "the word Adonai comes from a root meaning support for a pole of the tabernacle, so I often translate it as Foundation or Upholder."
As to the appellation Adonai, sometimes it denotes what is nameable  and admirable; but at other times, when the letter Daleth in it is doubled, and the word receives an initial
The word Adonai signifies Sovereign Creator of all things.
Whenever it occurs in the Hebrew Text, they substitute the word Adonai in its place.
Adonai, is very emphatic, and intimates a very awful sense of God's glorious majesty and a dread of his wrath.
Jacob; and my name Adonai have I not shown unto them. "
My name Adonai I did not show them ": David also said (Ps. 118: 100):