teixiptla.

Headword: 
teixiptla.
Principal English Translation: 

an image of someone, a substitute, or a delegate (see Molina); a ritual representative of a deity in religious ceremonies (see attestations); see also ixiptla

Alonso de Molina: 

teixiptla. imagen de alguno, sustituto, o delegado.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 95v. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

teixiptla = "...the term's condition of inherent possession and the fact of its (performative) embodiment direct us away from translations like 'representation,' which connotes a mental image or symbolic stand-in. A teixipla is the being whom s/he embodies; it is neither an impression nor a representation of that being.... Linguistically, materially, and mythohistorically, teixiptla literally tied flayed skins to god-bodies."
Sainthood and Race: Marked Flesh, Holy Flesh, eds. Molly H. Bassett and Vincent W. Lloyd (New York: Routledge, 2015).

"Words such as 'impersonator' or 'substitute' are only approximate translations of the Nahuatl term teixiptla. In the Nahuatl texts, teixiptla is used not only to describe living, moving cult performers (costumed persons), but also effigies of stone, wood, dough, or simply any assemblage of ritual attire on a wooden frame that included a mask [citing Hvidtfeldt 1958].... And for ritual purposes, of course, a teixiptla especially acted as a talismanic token of the sacred."
Richard F. Townsend, State and Cosmos in the Art of Tenochtitlan, Issues 20–24 (1979), 28.

"Teixiptla, those performed images that were transubstantiations of the deities themselves, are best known as the richly garbed 'deity performers' who played a central role in all Mexica ceremonies, as they did in the opening of the Acuecuexco aqueduct in 1499. Here, the most important presence was the teixiptla of Chalchiuhtlicue, a priest costumed as this deity, who stood at the aqueduct accompanied 'by all the priests of the temples,' who played flutes and blew on conch-shell horns to welcome the water into the city. His costume is carefully detailed in Durán's account...."
Barbara E. Mundy, The Death of Aztec Tenochtitlan, the Life of Mexico City (Austin: University of Texas Press, 2015), 66.

teixiptla = "flayed thing"
Jeanette Favrot Petersen, "Perceiving Blackness, Envisioning Power: Chalma and Black Christs in Colonial Mexico," in Seeing Across Cultures in the Early Modern World, eds. Dana Leibsohn and Jeanette Favrot Peterson (Burlington, VT: Ashgate, 2012), 67, note 48; citing Molly Bassett, personal communication, 2007.

"The terms for god-image were teixiptla and toptli. Teixiptla derived from xip, meaning 'skin, rind, or covering.' Toptli means 'covering or wrapping.' In a sense, gods fill up the human and natural images (rocks, trees, plants) that are thought to resemble them."
David Carrasco, City of Sacrifice: The Aztec Empire and the Role of Violence in Civilization (Boston: Beacon Press, 1999), 132.

auh yn tlamanj njman ic conquj yn iezço ymal, xoxoujc xicalli, tlatenpotonilli, vncan qujoaltequjlia, in tlamictique, ipan icatiuh piaztli no tlapotonilli. Auh njman ic vncã eoa in qujntlatlaqualia diablome, noujian nemj, izqujcan qujça acan qujmocauja, acan qujxcaoa in calmecac, calpulco: in teme teixiptlaoan, intenco qujmontlatlalilia yn jezço malli, piaztica qujmonpalotitiuh, tlaujcetinemj = And the captor thereupon took the blood of his captive into a green bowl with a feathered rim. The sacrificing priests came to pour it there. In it went the hollow cane, which also had feathers. And then the captor departed with it so that he might nourish the demons. He went into and came out of all [shrines]; he omitted none; he forgot not the priests dwellings in the tribal temples. On the lips of the stone images he placed the blood of his captive, giving them nourishment with the hollow cane. He went in festive attire. (16th century, Mexico City)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2—The Ceremonies, No. 14, Part III, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 52.

yn aqujn pepenaloia in teixiptla, atle yiaioca = He who was chosen impersonator was without defects. (16th century, Mexico City)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2—The Ceremonies, No. 14, Part III, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 64.