Ju·ras·sic 
(j-răsĭk)
(j-răsĭk)adj.
Of, relating to, or being the period of geologic time from about 200 to 146 million years ago, the second period of the Mesozoic Era, in which dinosaurs were the dominant form of terrestrial animal life, and the earliest birds appeared. See Table at geologic time.
n.
The Jurassic Period.
[French jurassique, after the Jura (Mountains).]