upsilon /ūp-sīˈlon, ŭp-, ūpˈsi- or upˈsi-/ or ypsilon /ip-sīˈlon or ipˈsi-/

1. The twentieth letter of the Greek alphabet (Υ, υ)
2. As a numeral υˈ = 400, ˌυ = 400000
3. A short-lived heavy subatomic particle produced when beryllium nuclei are bombarded with high-energy protons

• pile-worms
• pilewort
• pileworts
• pilfer
• pilferage
• pilferages
• pilfered
• pilferer
• pilferers
• pilferies
• pilfering
• pilferingly
• pilferings
• pilfers
• pilfery
• pilgarlick
• pilgarlicks
• pilgarlicky
• pilgrim
• pilgrimage
• pilgrimaged
• pilgrimager
• pilgrimagers
• pilgrimages
• pilgrimaging