The term 'Closed Tight' can be described by three different crossword solutions: SHUT (4 letters), SEALED (6 letters), and SEALEDUP (8 letters). SHUT is a verb meaning to close something firmly, usually with a door or window. SEALED is an adjective meaning to be closed or secured so that nothing can enter or escape. SEALEDUP is an adjective meaning to be completely closed or sealed off. All three words describe the same concept of something being securely closed.