intercalation
  置閏,插入
  In·ter·ca·la·tion n.
  1. Chron. The insertion of a day, or other portion of time, in a calendar.
  2. The insertion or introduction of anything among others, as the insertion of a phrase, line, or verse in a metrical composition; specif. Geol., the intrusion of a bed or layer between other layers.
     Intercalations of fresh-water species in some localities.   --Mantell.
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  intercalation
       n : an insertion into a calendar [syn: embolism]