to tell someone their faults to their face; or confess to have done something (see Molina)
IPAspelling:
iːʃkomɑkɑ
Alonso de Molina:
ixcomaca. nicte. (pret. onicteixcomacac.) dezir a alguno sus tachas, o faltas enla cara.
ixcomaca. nicn. (pret. onicnixcomacac.) confessar y conocer auer hecho algo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 45r. col. 1. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
ĪXCOMACA verfl, vt to confess to having done something; to tell another person his faults to his face, to give evidence / confesar y conocer haber hecho algo (M), decir a alguno sus tachas o faltas en la cara (M) comprueba (Z) [(3)Tp.143, (2)Zp.31,199]. In M this appears as a double transitive verb, taking a direct and an indirect object prefix, while it is attested as simply reflexive in T and transitive in Z and has to do with clarification, verification, and proof. See –ĪXCO, MACA.
ĪXCOMACALŌ nonact. ĪXCOMACA Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 112.