av(n = noun.time) ab - the eleventh month of the civil year; the fifth month of the ecclesiastical year in the Jewish calendar (in July and August);
is a kind of jewish calendar month
is a part of hebrew calendar, jewish calendar

   the eleventh month of the civil year; the fifth month of the ecclesiastical year in the Jewish calendar (in July and August). [WordNet 1.5]

av, abbr.
1 audiovisual (teaching aids etc.).
2 Authorized Version (of the Bible).

fast of av, ninth of av