1. (for non-buddhists) a fastday, a day of purification; (for Buddhists) a day on which lay-followers undertake to observe eight abstinence and on which they listen to teaching on the dhamma (usually the day preceding the nights of the new moon and the full moon, and the night midway between the two, i.e. the eighth, fourteenth and/or fifteenth days of the lunar fortnight; sometimes also the fifth day); the observance of this day; the abstinence undertaken on this day.
  2. the day on which the saṅgha assembles to confess any faults and to recite the pātimokkha q.v. (usually the fourteenth or fifteenth day of the lunar fortnight); the ceremony or (formal) act on this day.