vicennial /vī-senˈyəl/

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

• sweirnesses
• sweirt
• swelchie
• swelchies
• swell
• swell box
• swell boxes
• swelldom
• swelldoms
• swelled
• swelled head
• swelled-headed
• swelled heads
• sweller
• swellers
• swellest
• swell-headed
• swelling
• swellingly
• swellings
• swellish
• swell-mob
• swell-mobs
• swell-mobsman
• swell-mobsmen