# alidade-amplitude angle dihedral in betwixt a made-up phrase of words that have meaning but are meaningless in this combination. An alidade is an indicator or sighting apparatus used for measuring angles. Amplitude means "largeness, width, breadth or size." Dihedral is a mathematical term meaning "having or formed by two plane surfaces which meet along an edge." (An example of a dihedral angle is the angle formed by the pages of a book where they join along the spine.) Betwixt is an archaic word meaning "between."