Intercalate

Part of speech: verb (v.)

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. (Geol.), 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.