General antonyms:
* Disperse: To scatter or spread out.
* Dismiss: To send away or release.
* Adjourn: To suspend or postpone a meeting.
* Disband: To break up or dissolve a group.
* Scatter: To cause to separate and move in different directions.
Antonyms specific to meetings:
* Postpone: To delay or reschedule.
* Cancel: To call off or abolish.
The best antonym will depend on the specific situation you're describing.