Abarim Publications' online Biblical Hebrew Dictionary
According to BDB Theological Dictionary, the verb אדר (adar), originally meant to be wide or great, and began to mean "that which is superior to something else," as HAW Theological Wordbook of the Old Testament puts it.
In the Bible this verb is predominantly used in the meaning of to be majestic. It's frequently used in reference to God (Exodus 15:10, 1 Samuel 4:8, Psalm 93:4), but also His Law (Isaiah 42:21).
Our verb yields three derivatives:
- The masculine noun אדר (eder), meaning glory or magnificence (Zechariah 11:13), or, figuratively — in the sense of being wide — cloak (Micah 2:8).
- The adjective אדיר (addir), meaning majestic (Exodus 15:10, Judges 5:13).
- The feminine noun אדרת (aderet), meaning glory (Ezekiel 17:8) or, figuratively, cloak (1 Kings 19:13, Micah 2:8).