1. To insert, as a day or other portion of time, in a calendar.
2. To insert among others, as a verse in a stanza; specif.
(Science: geology) to introduce as a bed or stratum, between the layers of a regular series of rocks. Beds of fresh water shells . . . Are intercalated and interstratified with the shale. (Mantell)
Origin: L. Intercalatus, p. P. Of intercalare to intercalate to intercalate; inter between – calare to call, proclaim. See Calendar.