Principal English Translation: 

signal, sign, example, comparison, pattern, standard, insignia, mark, model (see Molina); the sign of the cross; a representation; a signature (see attestations)

Orthographic Variants: 
Alonso de Molina: 

machiotl. señal. comparacion, exemplo, o dechado.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 50v. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

MACHIYŌ-TL sign, example / señal, comparación, ejemplo o dechado (M) This is implied by the verb MACHIYŌTIĀ . See MAT(I), -YŌ . Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 128.

Attestations from sources in English: 

tictoLaLiLia tomachioL tofirma = we place here our rubrics and signatures (Zacualco, 1629) Beyond the Codices, eds. Arthur J.O. Anderson, Frances Berdan, and James Lockhart (Los Angeles: UCLA Latin American Center, 1976), Doc. 31, 196–197.

IZ. catqui. machiyotl = Here is an example (central Mexico, 1611)
Annals of His Time: Don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, James Lockhart, Susan Schroeder, and Doris Namala, eds. and transl. (Stanford: Stanford University Press, 2006), 178–9.

in citlalmachiyotl = the star sign; in colonial Nahua Theater, this refers to the Star of Bethlehem. (Metepec, Valley of Toluca, 1717)
In Citlalmachiyotl, The Star Sign: A Colonial Nahua Drama of the Three Kings, eds. Justyna Olko and John Sullivan, translation by Louise M. Burkhart (Warsaw: University of Warsaw, Faculty of "Artes Liberales", 2017), cover and pp. 1, 9.

Ic chiquacen capitulo, vncan mjtoa in nez, in mottac, in machiotl, ioan in tetzaujtl, in aiamo oalhuj españoles in njcan tlalli ipan, ioan in aiamo iximachoia, in njcan chaneque. = Sixth Chapter, in which it is told how signs and omens appeared and were seen, when the Spaniards had not yet come to this land, and when they were yet unknown to the dwellers here. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, 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), 17.

in nez, in mottac in machiotl yoā in tetzavitl = there appeared and were seen signs and omens 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), 50.

auh ca cenca miec in machiotl, yuan tlamahuiçolli omuchiuh ynic neci, in quenin cenca tlaçotli yn tetlapaloliztli in Aue Maria = and a great many signs and marvels occred by which it is evident how very precious is the greeting, the Hail Mary (late sixteenth century, Central Mexico)
Louise M. Burkhart, Before Guadalupe: The Virgin Mary in Early Colonial Nahuatl Literature, Institute for Mesoamerican Studies Monograph 13 (Albany: University at Albany, 2001), 133.

In tlauilli, in ocotl, in machiotl, in octacatl, in coyaoac tezcatl: mixpan nicmana. Inin tlatolli iechpa mitoaya: in aquin tecutlatoaya, in iuicpa maceoalli, in cenca qualli tlatolli iixpan = I set before you a light, a torch, a model, a measuring rod, a great mirror. This phrase was said of a lord who spoke to the people and placed before them excellent words. Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 150–151.

Attestations from sources in Spanish: 

…yn ompa colhuacatepec yn quichiuhque yn inezca yn inmachiyo = Allá en Colhuacatepec hicieron su signo, su señal. (Quauhtinchan, s. XVI)
Historia Tolteca-Chichimeca, eds. Paul Kirchhoff, Lina Odena Güemes, y Luis Reyes García (México: CISINAH, INAH-SEP, 1976), 171, 160.

amon quitlali ytoca ynmachiyo ypanpa zouatl = no escribio su nombre ni firmo porque es mujer (Tlaxcala, 1562)
Catálogo de documentos escritos en náhuatl, siglo XVI, vol. I (Tlaxcala: Gobierno del Estado de Tlaxcala y el Archivo Histórico del Estado de Tlaxcala, 2013), 18.

...'señal, ejemplo, dechado,' llegó a significar 'la señal de la cruz' y también 'firma.' Thelma Sullivan, Documentos Tlaxcaltecas del siglo XVI en lengua náhuatl (Mexico: Universidad Nacional Autónoma de México, 1987), 36.