Yantra is a Sanskirt word that means machine, to sustain energy, or a geometrical design intended to represent a deity or serve as a vehicle for the deity’s energy or Shakti storage. Yantras are effective tools used for meditation and increased awareness. One well-known example of a yantra is the Shri Yantra.

Further reading
Yantra by Rose Devi
Happy Holi from Taos! by Adityanath