a new word formed by joining two others and combining their meanings
<noun.communication> `smog' is a blend of `smoke' and `fog' `motel' is a portmanteau word made by combining `motor' and `hotel' `brunch' is a well-known portmanteau
a large travelling bag made of stiff leather
<noun.artifact>
Portmanteau \Port*man"teau\, n.; pl. {Portmanteaus}. [F. porte-manteau; porter to carry + manteau a cloak, mantle. See {Port} to carry, and {Mantle}.] A bag or case, usually of leather, for carrying wearing apparel, etc., on journeys. --Thackeray.
It was built into the policy for recognising Croatia and will prove entirely meaningless. There is a portmanteau phrase of the New Imperialism to cover all this: 'good governance.'