Open the Dictionaries dialog via Settings > Dictionaries in the navigation menu.

Select the dictionary you wish to delete, and click the Delete option in the dictionary's option menu.

NOTE: It is possible to select and delete multiple dictionaries at once, if required.

If the information in the confirmation dialog looks correct, click Yes to delete the selected dictionaries.

NOTE: There is no undo option. Deleted dictionaries cannot be recovered, and must be re-created from scratch.