- (italics) a Greek work on astronomy by Ptolemy.
- (lowercase) any of various medieval works of a like kind, as on astrology or alchemy.
- a work on astronomy compiled by Ptolemy in the 2nd century a.d containing a description of the geocentric system of the universe and a star catalogue
- (sometimes not capital) any of various similar medieval treatises on astrology, astronomy, or alchemy
late 14c., title of a treatise on astronomy by Claudius Ptolemy of Alexandria, extended in Middle English to other works on astrology or astronomy, from Old French almageste (13c.), from Arabic al majisti, from al “the” + Greek megiste “the greatest (composition),” from fem. of megistos, superlative of megas “great” (see mickle). Originally titled in Greek Megale syntaxis tes astronomios “Great Work on Astronomy;” Arab translators in their admiration altered this.