1. To insert between or among, primarily a day in the calendar.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• intercalady,
• intercalatry,
• untercalate,
• jntercalate,
• kntercalate,
• ontercalate,
• 9ntercalate,
• intercalates,
• intercalated,
• intercelate,
• interralate,
• inescaate,
• interjaculate,
• Interjiculate,
• interugulate,
• interunulate,
• intercalator,
• interclase,
• interamatate,
• Interceiptal

• Interlaken,
• intercom,
• interrelation,
• Interpol,
• interact,
• intertidal,
• intercourse,
• internal ear,
• internet,
• interlard,
• intergalactic,
• interpersonal,
• intercession,
• Intercessor,
• intervertebral,
• internalize,
• interrelate,
• intersexual,
• interlineal,
• interrogation,
• intersect,
• interconnect,
• interrogative,
• interpreter,
• inter alia,
• internal angle,
• interlace,
• intercostal,
• interchurch,
• interstate,
• intersectant,
• interpolate,
• interrupted,
• Interahamwe,
• interstratify,
• interpreted,
• interleave,
• intertribal,
• interchange,
• internecine,
• interlock,
• intricate,
• intermittent,
• interracially,
• international,
• interrogatory,
• in theory,
• interfacial,
• intermediate,
• interceptor,
• interior,
• interject,
• interval,
• interrogator,
• interested,
• internalise,
• interpellate,
• interest rate,
• interleukin,
• interlude,
• intermit,
• Interleaf,
• interracial,
• intercalary,
• interrelated,
• interrupter,
• intercalation,
• intermural,
• interdict,
• interlinear,
• interlaced,
• intercept,
• intercellular,
• internationale,
• interception,
• interplay,
• interior angle,
• interferometer,
• interpolation,
• interlayer,
• internal,
• interest,
• interface,
• interlope,
• interloper,
• intercede,
• interweave,
• intermediately,
• interrogate,
• in the raw,
• intercrossed,
• interlink,
• interfere,
• interlingua.

The adverb form of "intercalate" is "intercalatingly".

The adjective form of the word "intercalate" is "intercalary".