In order to rename the "Priorities" text in the issue navigator, you may need to edit the following properties file in the language pack:
The following property value in the Issuenavigator_en.properties:
Note that this has been changed in 4.3 and later.
Also note that this does not change Advanced search. See JRA-27414 - Add advanced search field names to i18 file Open .
The language pack is a JAR file located in
<jira-install>/atlassian-jira/WEB-INF/lib. For more information about Customizing Text in JIRA, please refer to Customizing Text.
For more information for JIRA 4.4+ please refer to the Renaming System Fields in JIRA JIRA Knowledge base article.