seal;  to seal (e.g. a letter);  to affix a seal;  to seal up
 to seal (letter);  to prevent;  to forbid;  to block
 blockade;  lockdown;  sealing off (an area);  freezing (funds)
 to shut in;  to confine;  to contain
 opening (a letter, parcel, etc.);  breaking the seal;  unboxing (a product);  unsealed mail
 muzzling (a person);  preventing (a person) from revealing something;  silencing (a person);  murdering (a person) to prevent them from revealing something
 suppression (e.g. of free speech);  force-out
 enclosing (e.g. with a letter)
 unopened (state);  with an unbroken seal
 to seal (letter);  to prevent;  to forbid;  to block
 seal (letters, documents, etc.)
 premiere;  first showing;  release (film)
 economic blockade;  embargo
 bill strap;  currency strap;  currency band;  wrapper band;  newspaper band
 to suppress the freedom of speech
 self-addressed stamped envelope;  SASE
 self-addressed stamped envelope;  SASE
 incantation to rid a child of insects traditionally believed to cause disease;  charm to cure colic, tantrums, etc.
 first-run theater;  first-run theatre
 window envelope;  billing envelope
 Japanese-style oblong, open end envelope
 return, postage-paid envelope
 diplomatic bag;  diplomatic pouch
 tumulus;  barrow;  grave mound
 landlocked variety (of fish)