Dorje, or Vajra, is applied to anything of an exalted religious character which is lasting, immune to destruction, occultly powerful and irresistible.
Evans-Wentz provides the canonical definitional thesis: dorje designates a quality of indestructible, irresistible sacred power applicable across deities, initiates, places, texts, and philosophical systems.
, The Tibetan Book of the Great Liberation, 1954thesis