vicennial /vī-senˈyəl/

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

• snaggle-toothed
• snaggy
• snags
• snail
• snail darter
• snail darters
• snailed
• snaileries
• snailery
• snailfish
• snailfishes
• snail flower
• snail flowers
• snailier
• snailiest
• snailing
• snail-like
• snail mail
• snail-paced
• 'snails
• snails
• snail-shell
• snail-shells
• snail-slow
• snail's pace