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

• counter-espionage
• counter-evidence
• counterexample
• counterexamples
• counterextension
• counterfactual
• counterfect
• counterfeisance
• counterfeit
• counterfeited
• counterfeiter
• counterfeiters
• counterfeiting
• counterfeitly
• counterfeits
• counterfesaunce
• counter-fleury
• counter-flory
• counter-flowered
• counterfoil
• counterfoils
• dealbation
• dealbations
• dealbreaker
• dealbreakers