The node form will not submit,if the word 'exit' is put in the title field I am using Drupal7, if the word 'exit' is entered into the text field, and the user submits/saves/previews the page, then the data is not submitted, saved, or previewed. The node edit page reloads and all changes are lost.

Is the word 'exit' a blacklisted word in node add/edit form?How can i over ride this prob?

Thanks in advance, Prem
No, Drupal doesn't have any word blacklists.

That logic must be caused by a custom or contributed module that you have installed (or even a theme I suppose). Try methodically disabling modules/themes until you find the culprit.

Starting with modules that provide text filters or alter the content body in some way would be the obvious places to start.