The fourth month of the ecclesiastic year (in June and July)

• The tenth month of the civil year

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1530s, from Hebrew tammuz , tenth month of the Jewish civil year, fourth of the sacred, covering parts of June and July; also the name of a Syrian deity equivalent to Phoenician Adon , whose festival began with the new moon of this month (compare Tammuz ...

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Thammuz \Tham"muz\, Tammuz \Tam"muz\, n. [Heb. thamm[=u]z.] A deity among the ancient Syrians, in honor of whom the Hebrew idolatresses held an annual lamentation. This deity has been conjectured to be the same with the Ph[oe]nician Adon, or Adonis. --Milton. ...