\In*ter`ca*la"tion\, n. [L. intercalatio: cf. F.
intercalation.]
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.