ThessalyPronunciation: /ˈθɛsəli/Definition of Thessaly a region of NE Greece. Greek name Thessalía /ˌθɛsaˈlia/. Derivatives ThessalianPronunciation: /θɛˈseɪlɪən/ adjective & noun Thessaly in other Oxford dictionaries Definition of Thessaly in the US English dictionary