The phrase "pure caffeine" refers to caffeine that does not contain any other substances or additives. It is simply caffeine in its natural form, without any additional ingredients. Full definition
«There's a perception that coffee won't give you the same benefits as pure caffeine,» he said. (sciencedaily.com)
«While there is a lack of high - quality research on coffee as a source of caffeine, there is an abundance of research on pure caffeine,» he said. (sciencedaily.com)
Since it's so concentrated (it's basically pure caffeine), even amounts that look small to you could be lethal. (health.com)