Yantra

sk यन्त्र yantra "sign", "diagram", "design", "device". | pa yant | kh យ័ន្ដ yan't "protective bareer"; សាក់យ័ន្ដ sakyant, "tattooed symbol".

In Shaivism, Yantra is a type of ritualistic worship performed along with Tantra and Mantra. While yantra is a mystical diagram charged with occult powers, tantra is mostly the worship of the female energy of Shiva, his Shakti, through mystical sexual intercourse, and mantra is a magical formula.
Mystical diagrams, usually small-sized and portable, with geometric patterns that can be two- or three-dimensional, while mandalas are mostly two-dimensional. It can be the form of a deity as a symbol.
In Buddhism, yantras are graphic symbols used in the recitation of the mantras and the dhāraṇīs.
In Cambodian traditions, yantras are magical diagrams used for protection. Healing kru (traditional doctors) drawn these "bareers" on cloth, metal foil or paper, or as tattoo. They often combine the five representations of the Buddha, the five corresponding pali letters, and symbols of Brahmanic origin (The Triple Gem). The former ones are often drawn in yellow, the latter in red.
The etymology of Prasat Bayon ប្រាសាទបាយ័ន has often been explained as Pa-Yan(t), "The Great Yantra" or "Ancestor's Yantra", the building being a kind of "diagram in stone."

Source