Almanac \Al"ma*nac\ (?; 277), n. [LL. almanac, almanach: cf. F. almanach, Sp. almanaque, It. almanacco, all of uncertain origin.]

A book or table, containing a calendar of days, and months, to which astronomical data and various statistics are often added, such as the times of the rising and setting of the sun and moon, eclipses, hours of full tide, stated festivals of churches, terms of courts, etc.

Nautical almanac, an almanac, or year book, containing astronomical calculations (lunar, stellar, etc.), and other information useful to mariners.

Source: Webster's Revised Unabridged Dictionary (1913)