intercalate

UK: /ɪnˈtɜːkəˌleɪt/ US: (in tûr′kə lāt′)

Inflections of 'intercalate' (v): (⇒ conjugate)

intercalates

v 3rd person singular

intercalating

v pres p

intercalated

v past

intercalated

v past p

WordReference Random House Unabridged Dictionary of American English © 2026

in•ter•ca•late  (in tûr′kə lāt′), v.t., -lat•ed, -lat•ing. 

1. to interpolate;
   interpose.
2. to insert (an extra day, month, etc.) in the calendar.

• Latin intercalātus past participle of intercalāre to insert a day or month into the calendar, equivalent. to inter- inter- + calā- (stem of calāre to proclaim) + -tus past participle suffix
• 1605–15

in•ter′ca•la′tive, adj. 
Synonyms

• 1. interject, introduce, insinuate.

Collins Concise English Dictionary © HarperCollins Publishers::

intercalate / ɪnˈtɜːkəˌleɪt/ verb (transitive)

1. to insert (one or more days) into the calendar
2. to interpolate or insert

Etymology: 17th Century: from Latin intercalāre to insert, proclaim that a day has been inserted, from inter- + calāre to proclaim

inˌtercaˈlation noun

inˈtercalative adjective