Certainly not someone who tries to be killed!
It seems that "martyrdom" has become fashionable in some parts of the world; but that title is mostly delusional.
The definition is probably more serious — and consequential — than simple English grammar. It's a matter of life & death, often a result of misguided thinking.
The Oxford dictionary says that a martyr is someone who is killed because of religious or other beliefs. But I take issue with this…when the person killed TRIED to be killed. Delusion doesn't qualify.
My take…a true martyr is someone killed as a CONSEQUENCE of promoting a belief, not someone who blows himself/herself up and kills others in the effort.
Going to heaven or nirvana is another matter. Perhaps the delusional aspect of the act.