Atma means the self or the soul. This is what we really are—the spiritual spark inside our body—as distinct from what we mistakenly think we are—our body and mind. Generally we think of ourselves in terms of the various labels we've had pinned on us—American, English, Christian, Hindu, white, black, liberal, conservative, father, mother, Jones, Smith, man, woman, or whatever. But these are only temporary tags. Time unpins them and replaces them with new ones. After all, the label is different from the merchandise.
Therefore, although atma sometimes refers to one's temporary body, mind, or intelligence, the atma is ultimately the eternal consciousness (the spirit, or soul) that is present within the body of every living being. This atma—higher than the senses, the mind, and even the intelligence—is most mysterious and subtle.
(Image illustrates that bodies may differ but all atmas (souls) are spiritually equal.)