Related Clues:

• Fastened shut
• Hermetic
• Closed tight
• Shut tight
• Not open
• Opposite of 18-Across
• Isolated, with "off"
• Like diplomatic pouches
• Seal tightly
• Enclosed tightly
• Closed tightly
• Slammed, maybe
• Word with ''in,'' ''up'' or ''down''
• Z's
• Shut tightly