It can never be fully disabled, unfortunately. You can clear your browser history (including all new history being cleared on session exit every time) and follow the below steps to get close to the desired results.
In older versions of chrome:
- Go to the Chrome menu on the browser toolbar
- Click Settings
- Click Show advanced settings (on the bottom)
- In the Privacy section, deselect the "Use a prediction service to help complete searches and URLs typed in the address bar" checkbox
In newer versions:
- From privacy section, click "Sync and Google services"
- Disable "Autocomplete searches and URLs"
Keep in mind that the address bar shows matches from your browsing history, in addition to predictions. If you don't want to see matches from your browsing history, you must clear that as well.
Beyond that there is nothing more you can do. It is either all or nothing. You cannot modify the behavior of how you dismiss suggestions. Suggestions and autocomplete are the same service.