CiviCRM Community Forums (archive)

Sadly, there's only one way to do this as an administrator, and it's a very blunt tool.  You can use the word replacements tool to replace all instances of "confirm contribution" with something else.  You'll find that in Administer - Customize Data and Screens - Word Replacements.  However, that will replace the text site-wide, including in places where it may be inappropriate to do so.  (People most commonly do this for something like replacing "Membership" with "Subscription", "member" with "subscriber", etc.)

If you're able to dig into the code, it's simple to change the text for some or all contribution pages by writing an extension (the preferred way) or doing a template override.  I'm also certain that it would be a welcome new feature in the core CiviCRM code to allow for custom contribution page (and event, petiion, and profile) buttons.