something scary, scandalous or a very serious crime (see Molina)
IPAspelling:
mɑkɑʃok
Alonso de Molina:
macaxoc. cosa espantosa, o escandalosa, o delito grabisimo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 50r. col. 1. Thanks to Joe Campbell for providing the transcription.