[fleitz]

If you walk away with your life you're by definition not a martyr.

[cobrausn]

Nitpicking. People are often called 'martyr for a cause' if they end up persecuted or imprisoned.

http://www.merriam-webster.com/dictionary/martyr

Definition #2. It helps if you die, but it's not required.

[Dove]

Actually, if you'll look at the wikipedia article about the term and its history, you'll see that it has several meanings. Dying isn't always required.