As defined in the article: "when a computer is reset without following proper procedures (what’s known as a cold/hard reboot)"

Even if you disagree, "cold boot attack" is the established name for the actual attack, the new aspect presented here is how to circumvent a certain firmware protection that would overwrite the memory on a cold boot to prevent that attack.

If you would give your definition we could see if it is right, too.

Cold boot attack: An attack in which a running system is reset and information extracted from its memory that survived the reset. Seems like the article is using it correctly.