nacaztli.

Headword: 
nacaztli.
Principal English Translation: 

ear(s) (see Molina, Karttunen); corner, side (see Lockhart)

Orthographic Variants: 
nacastli
IPAspelling: 
nɑkɑstɬi
Alonso de Molina: 

nacaztli. oreja.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 062v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

NACAZ-TLI ear / oreja (M)
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 156.

Lockhart’s Nahuatl as Written: 

ear, corner, side. 226
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 226.

Attestations from sources in English: 

ca much vncā [fol.31] icuiliuhtoc in tzontecomatl, nacaztli, iollotli, cuitlaxculli eltapachtli, tochichi, macpalli, xocpalli = for there were painted all severed heads, ears, hearts, entrails, livers, lungs, hands and feet (Mexico City, sixteenth century)
James Lockhart, We People Here: Nahuatl Accounts of the Conquest of Mexico, Repertorium Columbianum v. 1 (Los Angeles: UCLA Center for Medieval and Renaissance Studies, 1993), 128.

vel xitlacaquican, vel xinacaçocan, tlein quitoz, vel nacaztli in anquioalcuizque = listen well, make good use of your ears, bring back in your ears a good record of what he says
James Lockhart, We People Here: Nahuatl Accounts of the Conquest of Mexico, Repertorium Columbianum v. 1 (Los Angeles: UCLA Center for Medieval and Renaissance Studies, 1993), 64.

o-te-nacas-tec (tequi) = people's ears were cut off (Anales de Puebla)

tonacaz / tlacaqui. / ycavaca = Our ears: They hear, they ring (central Mexico, sixteenth century)
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 255.

ynic pati. cuechtli michiqui motecã tonacazco yoã oxiayutl (central Mexico, sixteenth century)
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 285.

çan tiquinyacatequizq. / yhuan tiquinnacaztequizq. ye tiquinpohuazq. ye tiquinpohuazq yn tomalhuan auh yehica cecentlapal yn quintequiliq yn innacaz = we shall only cut off their noses and their ears. Now we shall count them as our captives. And it was for this that they cut off their ears on both sides [of the head].
Codex Chimalpahin: Society and Politics in Mexico Tenochtitlan, Tlatelolco, Culhuacan, and Other Nahuatl Altepetl in Central Mexico; The Nahuatl and Spanish Annals and Accounts Collected and Recorded by don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, eds. and transl. Arthur J. O. Anderson and Susan Schroeder (Norman: University of Oklahoma Press, 1997), vol. 1, 226, 227.

Toyomotlan, tonacaztitech mopipiloa in totecuyo. Inin tlatolli, itechpa mitoaya: in iquac itla topan quimuchiuilia totecuyo: azo cetl quiqua in tonacayotl, azo mayanaliztli. = Our Lord is pinching our ribs and pulling our ears. This was said when our Lord caused some such thing to befall us as a frost which ravaged the crops, or a famine.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 172–173.

nacazquauhiotl = ear cartilage
tonacazquauhio = our ear cartilage (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, 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, 1961), 113.

nacaztepetlati = he is hard of understanding
nacazqualo = ear aches (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, 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, 1961), 113.

monacazquetza = listen attentively, literally "rise up at the ears" -- "Since the third-person reflexive prefix mo- is incorporated into the sign value for a reflexive verb, the pertinent logographic values in this case is MONACAXQUETZ(A)." This example of an "eavesdropper and scandalmonger" comes from the Codex Mendoza, folio 70 recto.
Gordon Whittaker, Deciphering Aztec Hieroglyphs, 2021, 107.

Attestations from sources in Spanish: 

in tennecuiltzin, in ixpopoyotzin, in ixpatzactzin, ahnozo macuecuetzin, matzicoltzin, matohpoltzin, ahnozo huilatzin, xotepoltzin ahnozo imatzin, icxitzin quihuilana, ahnozo nontzin, nacaztapaltzin = del de boca torcida, del ciego, del tuerto o del manco, del lastimado de la mano, del que tiene la mano cortada o del tullido que anda a gatas, del cojo, del que arrastra el pie o la mano o del mudo, del sordo
Huehuehtlahtolli. Testimonios de la antigua palabra, ed. Librado Silva Galeana y un estudio introductorio por Miguel León-Portilla (México: Secretaría de Educación Pública, Fondo de Cultura Económica, 1991), 58–59.