to unload or to lighten a boat or ship (see Molina)
Alonso de Molina:
atlan tlaza. nitla. (pret. onitlaatlantlaz.) alijar nauio. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 8r. col. 2. Thanks to Joe Campbell for providing the transcription.