chapani.

Headword: 
chapani.
Principal English Translation: 

to get very wet; or for the dough to fall on the ground; mud; or, for there to be a slapping sound like dough falling on the ground or wet clay (see Karttunen and Molina); or, to droop (see Molina)

IPAspelling: 
tʃɑpɑːni
Alonso de Molina: 

chapani. ni. (pret. onichapan.) mojarse mucho, o caer en tierra la massa, el lodo o cosas semejantes.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 19r. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

CHAPĀN(I) for there to be a slapping sound like falling dough or wet clay / mojarse mucho, o caer en tierra la masa, el lodo o cosas semejantes (M), el ruido del barro y masa, que cae en el suelo (C)
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 46.

Attestations from sources in English: 

chapani = it droops (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 95, 97.

themes: 
Sensory Perception (sound, smell, etc.)