SG Heritage Dictionary

Intercalation [Noun] Webster's Dictionary 1828

The insertion of an odd or extraordinary day in the calendar, as the 29th of February in leap year.

Intercalation [Noun] Webster's Dictionary 1913

1. 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.

Interposition Roget’s Thesaurus §228

N. interposition, interjacence, intercurrence, intervenience, interlocation, interdigitation, interjection, interpolation, interlineation, interspersion, intercalation, interpenetration, permeation, infiltration, intervention, interference, intrusion, obtrusion, insinuation, insertion, dovetailing, embolism, intermediary, intermedium, go between, bodkin|, intruder, interloper, parenthesis, episode, flyleaf, partition, septum, diaphragm, midriff, dissepiment, party wall, panel, room divider, halfway house

V. lie between, come between, get between, intervene, slide in, interpenetrate, permeate, put between, introduce, import, throw in, wedge in, edge in, jam in, worm in, foist in, run in, plow in, work in, interpose, interject, intercalate, interpolate, interline, interleave, intersperse, interweave, interlard, interdigitate, sandwich in, fit in, squeeze in, let in, dovetail, splice, mortise, insinuate, smuggle, infiltrate, ingrain, interfere, put in an oar, thrust one's nose in, intrude, obtrude, have a finger in the pie, introduce the thin end of the wedge, thrust in

Adj. interjacent, intercurrent, intervenient, intervening, intermediate, intermediary, intercalary, interstitial, embolismal, parenthetical, episodic, mediterranean, intrusive, embosomed, merged

Adv. between, betwixt, twixt, among, amongst, amid, amidst, mid, midst, in the thick of, betwixt and between, sandwich-wise, parenthetically, obiter dictum