Both Uses of

medieval
in
Fast Food Nation

The long chemical names on the little white labels were as mystifying to me as medieval Latin.†
p. 122.2 *

The fast food joints along the Strip seem insignificant compared to the new monuments towering over them: recreations of the Eiffel Tower, the Statue of Liberty, and the Sphinx, enormous buildings that evoke Venice, Paris, New York, Tuscany, medieval England, ancient Egypt and Rome, the Middle East, the South Seas.†
p. 235.6

Definitions:

(1) (medieval)
relating to or belonging to the Middle Ages

(The period of European history beginning with the fall of the Roman Empire and followed by the Renaissance -- roughly 500-1500 AD)

Often thought of as a time of instability, superstition, plagues, feudal lords, and knighthood.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely, medieval may be used to refer to something as old-fashioned and unenlightened.