Explaining complex terms

I'm working on a financial services project, which includes a questionnaire. Some of the terms used in this questionnaire are financial and won't make sense to some users , but in order to explain what they mean, the length of the question would double, making the question very long indeed. Having a lot of copy on the page is not desirable as it will discourage people from using the tool. As a way of managing this complexity, we are considering:

• A glossary that defines terms, but which would take the user away from the questionnaire
• Hover copy that would use a dashed underline to indicate to the user that an explanation is available
• Biting the bullet and including the explanation in the question

Which approach would you use and why? And is there another possibility?