Principal English Translation: 

to wash

Alonso de Molina: 

paca. nitla. (pret. onitlapacac vel. onitlapac.) lauar algo, o batanar paños o sayales.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 78v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

PĀC(A) vrefl.vt to bathe; to wash, launder something / se lava, se asea (T), lavar algo o batanar paños o sayales (M) In a section on the preterits of verbs represented by MACA and TOCA which retain their stem-final vowels, C points out that PAC(A) follows the rules of vowel-dropping but leaves it open that it may have an alternate preterit PĀCAC (Cf.31v). M gives alternative preterits -PĀC and -PĀCAC for TLAHTLAPĀC(A) 'to wash something repeatedly.' This verb preserves the Proto-Uto-Aztecan initial *P which has been lost in Ā-TL 'water, liquid.'PĀCALTIĀ caus. PĀC(A).PĀCALO altern. nonact. PĀC(A). PĀCŌ altern. nonact. PĀC(A). Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 182.

Lockhart’s Nahuatl as Written: 

nic. Class 1: ōnicpācac. 228
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), 228.

Attestations from sources in English: 

Nepācōc, neximalōc = People washed and shaved (themselves)Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 145.

ompa motlahtocapacato yn Don diego tehuetzquititzin = There don Diego Tehuetzquititzin went to be bathed as ruler. (central Mexico, early seventeenth century)
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, 172–173.