lunation Meaning, Definition & Usage

  1. noun the period between successive new moons (29.531 days)
    synodic month; lunar month; moon.

WordNet

Lu*na"tion noun
Etymology
Cf. Lunated.
Definitions
  1. 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.

Webster 1913