tentetl.

Headword: 
tentetl.
Principal English Translation: 

a lip plug (literally, lip stone)
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 172.

Might be made of green stone, turquoise, shells, obsidian, coral, gold, etc. (see attestations)

IPAspelling: 
teːntetɬ
Alonso de Molina: 

tentetl. bezote de indio.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 99v. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

temalacatentetl teuxiujtl coztic teucujtlatl icallo, chalchiuhtencololli, coztic teucujtlatl icallo, chalchiuhquauhtentetl, coztic teucujtlatl itzincallo = A disc-shaped lip plug of fine turquoise in a gold setting; A curved, green stone lip plug in a gold setting; A green stone lip plug in the form of an eagle, fitted at the base in a gold setting. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, 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, 1951), 27.

in jntenteuh in tlatoque chalchiuhtentetl, anoço tecciztentetl, anoço teocujtlatentetl. = The lip plugs of the rulers were green stone lip plugs, or sea shell lip plugs, or gold lip plugs. (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), 177.

teocuitlatentetl = golden lip plug
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 172.

teocuitlatempilolli = golden lip pendant;
cuauhtempilolli coztic teocuitlatl = a golden lip pendant in the form of an eagle;
teocuitlacuauhtentetl = golden eagle lip plug;
apatlactempilolli coztic teocuitlatl = lip pendant of gold in the form of a broad-leafed water plant;
ahuictempilolli coztic teocuitlatl = gold lip plug in the form of a boating pole;
atototempliolli coztic teocuitlatl = gold lip plug in the form of a pelican;
metztempilolli coztic teocuitlatl = crescent-shaped lip pendant of gold;
xiuhcoatempilolli coztic teocuitlatl = gold lip pendants in the form of a fire serpent;
apozonaltentetl = amber lip plugs;
chalchiuhtentetl = green stone labret;
xiuhtentetl = turquoise lip plug;
xoxouhqui tenzacatl = blue labret;
tehuilotentetl = lip plug of rock crystal;
itztentetl = obsidian lip plug;
tepochtentetl = lip plug of smoky stone;
tecciztentetl = seashell lip plug;
tapachtentetl = coral shell lip plug
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 173, 174, 175.

in tetepeiotl, in xivitzolli, in matemecatl, in cotzeoatl, in nacochtli, in tentetl, in tlalpilonj = the peaked cap, the turquoise diadem, the arm band, the band for the calf of the leg, the ear plug, the lip rod, the head band (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, 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), 57.

auh injc macho in telpuchpan povi, motexapotla, injc vncan motentetia = And to make it known that he belonged to the telpochcalli, the [lower] lip was pierced in order to place the lip plug there (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, 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), 209.

Attestations from sources in Spanish: 

teocuitlatentetl = beçoleros de oro (Tezozomoc)
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 172.