This paper discusses two environments in which concept definitions are published, namely terminological dictionaries which deal specifically with technical subjects and general online encyclopaedias such as Wikipedia. It compares the intended function of both resource types, justifies and explores their differences, and considers whether a mutually beneficial relationship can exist between both knowledge formats. This discussion will focus on a real world exercise undertaken to enrich term entries and definitions relating to the natural world in Welsh terminological dictionaries. The paper also investigates the technological methods used to incorporate Wiki content into terminological dictionaries, and examines some of the licensing issues arising from sharing content between different resources. It concludes by examining how the interconnection between the environments of Welsh Wicipedia and of Welsh terminological dictionaries might be developed in the future.