an oil stain, or a stain from lard, or something very greasy
IPAspelling:
tʃijɑktik
Alonso de Molina:
chiyactic. mancha de azeite o de manteca, o cosa llena de grassa. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 20v. col. 2. Thanks to Joe Campbell for providing the transcription.