Glory can be defined. In my research I discovered that it means a desirable brightness that is very rare!
a. The International Standard Bible Encyclopedia states this about Glory - FROM THE HEBREW WORD KĀBHŌDH.
i. The fundamental idea of this root seems to be “weight,” “heaviness,” and hence in its primary uses it conveys the idea of some external, physical manifestation of dignity, preëminence or majesty. At least three uses may be distinguished: (1) It defines the wealth or other material possesions which give honor or distinction to a person; (2) The majesty, dignity, splendor or honor of a person; (3) most important of all, it describes the form in which Yahweh (Jehovah) reveals Himself or is the sign and manifestation of His presence.