To reject or ignore:
* Ignore
* Disregard
* Overlook
* Neglect
* Brush aside
* Wave off
To end a meeting or employment:
* Discharge
* Fire
* Lay off
* Terminate
* Adjourn
* Conclude
* End
To send away:
* Release
* Expel
* Eject
* Banish
* Evict
* Escort out
To think of someone or something as unimportant:
* Despise
* Contemn
* Scorn
* Disdain
* Devalue
* Minimize
Other:
* Reject
* Refuse
* Repudiate
* Abolish
* Annul
The best synonym will depend on the specific situation and the desired effect. For example, "dismiss" might be replaced with "discharge" in a formal work setting, or with "ignore" in a personal conversation.