Principal English Translation: 

1) a long spiraling shell (see Molina); we know from an example of a necklace made of seven of these shells that is is not a large as a conch, which was used for trumpeting;
2) residue (see Karttunen)

Alonso de Molina: 

cuechtli. cierto caracol largo.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 25v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

In the second definition of this term, "This is the second element of CALCUĒCH–TLI 'soot' and CUAUHCUĒCH–TLI 'sawdust' and apparently means 'residue.' It contrasts in meaning and possibly in phonological form with M's cuechtli, which refers to a type of snail or spiral shell."