Intercalary /(?; 277)/

In·ter·ca·la·ry

Intercalary

a.
  1. 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. (Chron.)
  2. Introduced or inserted among others; additional; supernumerary.
    This intercalary line . . . is made the last of a triplet.
    — Beattie.

Phrases & Compounds

Intercalary day
one on which no paroxysm of an intermittent disease occurs.