Definition of "undecennary" []

• Once every eleven years; undecennial. (adjective)

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• "Cool word of the day: undecennary, which means "a period of eleven years" or "an eleventh anniversary.""
• "Japanese-American internment: the US army announced that it would no longer hold Japanese-Americans in Harold Holt: the Australian prime minister went missing and was presumed drowned while swimming off the coast of UFOs was terminated; the conclusion was that sightings were due to mass hysteria, hoaxes, mistakes and the like (1969) undecennary"