a large umbrella, something that provides shade (see Molina)
IPAspelling:
tsɑkwilwɑːstɬi
Alonso de Molina:
tzacuilhuaztli. moxcador grande, para hazer sombra. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 151v. col. 1. Thanks to Joe Campbell for providing the transcription.