In looking more closely at the lettering based on the comments here, I'd say it almost certainly seems to be showing ātmatattvam.
The word is found in Śrīmad-Bhāgavatam 5.5.5 and according to this site, also in the Upanishads:
which translates it as "the true nature of the soul or of the supreme spirit S3vetUp."
Gavin Flood -- is he on this list? -- talks about it in The Concept of Mind in Hindu Tantrism which can be found as a pdf via Google.
So it seems to be a consistent representation of a tantric yantra and mantra associated with ātmatattvam.
The appeal of such a tattoo to a young seeker of Indian wisdom is clear.
Best,
Dean