Yantra, mantra, tantra - it is important to understand the meaning of each. A mantra is a set of sacred syllables, which, when spoken with reverence may invoke a particular deity. Tantra is the systematic use of the body and mind - lower energies - to attain a higher function; 'from sex to superconsciousness'. And a yantra is the use of a symbol, or some kind of external object, as a tool for contemplation, concentration or meditation. In fact, any practice that is ritualistic or symbolic is part of the yantric approach.
The tattoo on Angelina Jolie's left shoulder is reported to be a yantra tattoo.