Undecimber

name

name ·Rare ·Advanced level

Definitions

Proper Noun
  1. 1
    A fictitious thirteenth month of the Western calendar.

Etymology

From Latin undecim (“eleven”); formed as logical continuation to December, which in its turn is derived from Latin decem (“ten”), as it was the tenth month in the Roman calendar. It is unclear whether the term was ever used in Classic Latin as a name for an intercalary month.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.