for wheat (or other foods) to become withered or frostbitten (see Molina)
Orthographic Variants:
patzac uaqui
Alonso de Molina:
patzac uaqui. (pret. opatzac uac.) añublarse el trigo. &c desta manera. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 80r. col. 2. Thanks to Joe Campbell for providing the transcription.