Al·ma·gest 
(ălmə-jĕst′)
(ălmə-jĕst′)n.
1. A comprehensive treatise on astronomy, geography, and mathematics compiled by Ptolemy about AD 150.
2. almagest Any of several medieval treatises concerned with astronomy or alchemy.
[Middle English almageste, from Old French, from Arabic al-majisti : al-, the + Greek megistē (suntaxis), greatest (composition), feminine of megistos, greatest, superlative of megas, great; see meg- in the Appendix of Indo-European roots.]