In chronology, inserted into the diary regarding regular purchase, as an additional time or thirty days; having an extra day or thirty days, as one of a cycle of many years.
therefore Inserted or coming between other people; introduced or current interstitially: as, intercalary beds in geology.
In biology, intermediate in character between 2 types, yet perhaps not representing the hereditary passage from a single form to the other; interposed or intercalated, yet maybe not biologically transitional.
In medication, the days intervening between the important days or crises of a disease.
In physiology, additional; supernumerary; inserted between the rest, as cartilages regarding dorsal region of the vertebral column in lots of elasmobranchs.