vicennial /vī-senˈyəl/

1. Lasting, or coming at the end of, twenty years
2. Occurring every twenty years

• nimmers
• nimming
• nim-oil
• nimonic
• Nimrod
• nims
• nincom
• nincompoop
• nincompoops
• nincum
• nine
• nine days' wonder
• nine-eleven
• nine-eyes
• ninefold
• nine-foot
• nine-hole
• nineholes
• personating
• personatings
• personation
• personations
• personative
• personator
• personators