noun (n)

• the period between successive new moons (29.531 days)(noun.time)

  Synonym:
  lunar month, moon, synodic month
  

  source: wordnet30
• The period of a synodic revolution of the moon, or the time from one new moon to the next; varying in length, at different times, from about 29¼ to 29⅚ days, the average length being 29 d., 12h., 44m., 2.9s.(noun)

  source: webster1913