If "bulletin" refers to a brief announcement:
* Denial: This suggests a formal rejection or contradiction of a statement.
* Suppression: This implies actively preventing information from being released.
* Silence: This denotes a complete lack of communication.
If "bulletin" refers to a periodical publication:
* Personal letter: This is a more informal and private communication.
* Book: This is a longer, more detailed piece of writing.
* Manuscript: This refers to a written document before it is published.
If "bulletin" refers to a specific type of publication (e.g., weather bulletin):
* Personal diary: This is a private record of personal experiences.
* Novel: This is a fictional narrative.
Ultimately, the best antonym for "bulletin" depends on the specific context and the intended meaning.