\In*ter"ca*la*ry\ (?; 277), a. [L. intercalaris,
intercalarius: cf. F. intercalaire. See {Intercalate}.]
1. (Chron.) 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.
2. Introduced or inserted among others; additional;
   supernumerary. ``Intercalary spines.'' --Owen.
         This intercalary line . . . is made the last of a
         triplet.                              --Beattie.
{Intercalary day} (Med.), one on which no paroxysm of an
   intermittent disease occurs. --Mayne.