a fresh, cool place, such as a green field that is irrigated (see Molina)
IPAspelling:
tɬɑseliɑːjɑːn
Alonso de Molina:
tlaceliayan. lugar fresco, assi como prado verde que se esta riendo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 116r. col. 2. Thanks to Joe Campbell for providing the transcription.