INTERCALARY a. 2 definitions
Inserted or introduced among others in the calendar; as, an intercalary month, day, etc.; -- now applied particularly to the odd day (Feb. 29) inserted in the calendar of leap year. See Bissextile, n.
INTERLINEAL; INTERLINEAR a.
Contained between lines; written or inserted between lines already written or printed; containing interlineations; as, an interlinear manuscript, translation, etc. -- In`ter*lin"e*ar*ly, adv.