In chronology, inserted in the calendar out of regular order, as an extra day or month; having an additional day or month, as one of a cycle of years.Hence Inserted or coming between others; introduced or existing interstitially: as, intercalary beds in geology.In biology, intermediate in character between two types, yet not representing the actual genetic passage from one form to the other; interposed or intercalated, yet not biologically transitional.In medicine, the days intervening between the critical days or crises of a disease.In anatomy, additional; supernumerary; inserted between other parts, as the cartilages on the dorsal side of the vertebral column in many elasmobranchs.