from
The Collaborative International Dictionary of English v.0.48
Intercalation \In*ter`ca*la"tion\, n. [L. intercalatio: cf. F.
intercalation.]
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1. (Chron.) The insertion of a day, or other portion of time,
in a calendar.
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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.
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Intercalations of fresh-water species in some
localities. --Mantell.
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