Thayer's Greek Lexicon

 1. a fasting, fast
  1) a voluntary, as a religious exercise
1a1. of private fasting
1a2. the public fast as prescribed by the Mosaic Law and kept
yearly on the great day of atonement, the tenth of the
month of Tisri (the month Tisri comprises a part of our
September and October); the fast accordingly, occurred in
the autumn when navigation was usually dangerous on
account of storms
  2) a fasting caused by want or poverty