to whistle (or make a whistling effect) with the hands and mouth (see Molina)
IPAspelling:
mɑːtɬɑpiːtsɑ
Alonso de Molina:
matlapitza. ni. (pret. onimatlapitz.) silvar con las manos y boca. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 53r. col. 2. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
MĀTLAPĪTZ(A) to make a whistle with the hands and mouth / silbar con las manos y boca (M) [(3)Tp. 165]. See MĀ(I)-TL, PITZ(A).
MĀTLAPĪCHILIĀ applic. MĀTLAPĪTZ(A) Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 139.