intercalation

In*ter`ca*la"tion, n. Etym: [L. intercalatio: cf. F. intercalation.] 1. (Chron.) Defn: 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.

---