Is it suicide if you do it to save other people?

Okay…no alarm bells here, Fluther. This question came up after a random discussion on a Chernobyl fan group, where we were discussing Legasov’s hanging himself, and someone said he would have gone to he’ll because suicide is a mortal sin.

It made me start thinking about how suicide is defined. Let’s say someone is being shot at and you dive in front of them to take the bullet instead, fully knowing you’ll be killed…is that considered suicide?

Valery Legasov hung himself, probably somewhat out of despair from being isolated from his friends and knowing he was slowly dying from cancer/radiation. But he also did it to get the word out about the inherent danger of RBMK reactors such as they were at the time, and, as a result of his death, changes were finally made that potentially saved countless lives.

So…what do you think?