Report on British fossil reptiles. Part II. In: Report of the eleventh meeting of the British Association for the Advancement of Science, held at Plymouth, July 1841, pp. 60-204.

In this review article Owen coined the term Dinosaur (pp. 102-103). In surveying fossil bones and teeth found by Gideon Mantell, William Buckland, and others, he observed that three genera--Iguanodon, Megalosaurus, and Hylaeosurus--shared similarities in the structure of their vertebrae and elephant-like posture. For this reason Owen classified them as a sub-order in the Saurian order, and called them Dinosauria, meaning terrible lizards. Digital facsimile from Biodiversity Heritage Library at this link.