Definition of grail
- grail Noun The Holy Grail.
- grail Noun The object of an extended or difficult quest.[http://www.merriam-webster.com/dictionary/grail]
- grail Noun GRAIL mission, an acronym for "Gravity Recovery and Interior Laboratory", a pair of NASA spacecraft sent to the moon to measure its gravity field.
- grail Noun A book of offices in the Roman Catholic Church; a gradual.
- grail Noun Small particles of earth; gravel.