I couldn't disagree more. "Self interested" absolutely does not have a well understood meaning in casual, every-day conversations. It's one of the most ambiguous terms out there.
Try this out: at a dinner party (one that you don't care if you're invited back), declare that "all people act out of self-interest, ultimately."
Odds are good that two people will disagree quite vehemently about this, and at the core will be a fundamental disagreement about what it means to be "self-interested".
Calling into question the meaning of "self-interested" is merely a filibuster.