pilchihua.

Principal English Translation: 

to commit a sin, to commit a fault (see Molina)

Orthographic Variants: 
pilchiua
IPAspelling: 
piltʃiːwɑ
Alonso de Molina: 

pilchiua. nitla. (pret. onitlapilchiuh.) pecar o hazer algun defecto.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 81v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

PILCHĪHU(A) vt to commit a sin / pecar o hacer algún defecto (M) [(1)Bf.9v]. See CHĪHU(A).
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 195.

Attestations from sources in English: 

itlahtlacol, in itlapilchihual = his sin
Susanne Klaus, Uprooted Christianity: The Preaching of the Christian Doctrine in Mexico, Based on Franciscan Sermons of the 16th Century Written in Nahuatl (Bonn: Bonner Amerikanistische Studien e. V. c/o Seminar für Völkerkunde, Universität Bonn, 1999), 249.

titlahtlacozque, yc titlapilchihuazque = we will commit sins Susanne Klaus, Uprooted Christianity: The Preaching of the Christian Doctrine in Mexico, Based on Franciscan Sermons of the 16th Century Written in Nahuatl (Bonn: Bonner Amerikanistische Studien e. V. c/o Seminar für Völkerkunde, Universität Bonn, 1999), 248.