I hate to use this word again but it "depends."
Some of the concepts that can be included are "not selfish," "care about others," "benefit others without benefiting self," or "doing good for others."
It depends on the context of how it's being used.
If you're trying to describe a person as altruistic, then go ahead and describe that person's behaviors and attitudes that fit the definition of altruism.
"She is a kind person who uses her time, resources and energy to help other people with no expectation or desire for reward or praise." (example)
For altruistic groups:
"An altruistic society is one that...."
For an academic use:
"The theory of altruism is that...."
One English word sometimes requires more than one sign, and vice verse. Sometimes one sign requires many English words. There isn't always a one-for-one match.