to be full of oneself, presumptuous, haughty (see Molina)
Orthographic Variants:
acçan ninomati
Alonso de Molina:
acçan ninomati. tenerse en mucho con presuncion y altiuez. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 2r. col. 1. Thanks to Joe Campbell for providing the transcription.