blue jean
/bluː ˈdʒiːn/adjective
1Made of a type of heavy blue twilled cotton cloth, typically used for work clothes (now usually denim). Also figurative : †dull, plain, ordinary ( obsolete ).
2Characterized by or wearing blue jeans.
noun
A heavy blue twilled cotton cloth, typically used for work clothes; blue denim.
Origin
Early 19th century. From blue + jean. Compare slightly earlier blue jeans.