tecciztli.

Headword: 
tecciztli.
Principal English Translation: 

conch shell(s), the kind used as a trumpet (see Karttunen); a large shell (see Molina); egg(s); eggshell(s); seashell(s); can also mean testicle in contemporary Eastern Huastecan Nahuatl (see IDIEZ fields)

IPAspelling: 
teːksistɬi
Alonso de Molina: 

tecciztli. otro caracol grande.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 92r. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

TĒCCIZ-TLI conch, the shell of which was used as a trumpet, or shell in general; egg / caracol grande (M) [(1)Cf.85r].
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 215.

Attestations from sources in English: 

yn centetl nicantotoltecciztli etetl cacavatl ipatihv yn castil ytecciz ontetl cacavatl ypatihv = One turkey egg is worth 3 cacao beans. A chicken egg is worth 2 cacao beans. (Tlaxcala, 1545)
Beyond the Codices, eds. Arthur J.O. Anderson, Frances Berdan, and James Lockhart (Los Angeles: UCLA Latin American Center, 1976), Doc. 1, 210–211.

in mopitza tecciztli, yoan acatecciztli = conch shells and reed pipes were blown (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2 -- The Ceremonies, no. 14, Part III, 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), 83.

Conch shells (tecciztli) are given as some of the essential items found in the "devil's houses" (Sahagún).
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 117.in ie iuhquj njman tlapitzalo, tecciztli mopitza, qujqujztli, mapipitzoa, yoan cujco: cujcapan tlapitzalpan, in oalmoiacatia: motecpana in cozcateca, qujquequechpanotiuj, aztapanjtl, qujiaoaloa in temalcatl = When this was done, then trumpets were sounded; conch shells, large sea shells, were blown; men put their fingers in their mouths and whistled, and there was singing. With singing of songs and blowing of trumpets, they arrived. The Cozcateca placed themselves in order, their shoulders decked with feather banners, and they encircled the offering-stone. (16th century, Mexico City)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2—The Ceremonies, No. 14, Part III, 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), 50.

IDIEZ morfema: 
tēcciztli.
IDIEZ traduc. inglés: 
1. the egg of any kind of bird, chicken, turkey. 2. s.o. or s.t.ʻs testicle.
IDIEZ def. náhuatl: 
1. Ce tlamantli tolontic tlen quiquixtia ce tlahpiyalli zo tecuani quemman tlamayohui; quipiya icacahuayo chipahuac, iiztacca chipahuac huan ixochiyo coztic. “Noconeuh nicnahuatihqui ma quicohuati tecciztli; quemman mocuapayayaya huetzico huan quipitzinih.” 2. no. Ce achi tlen itzintenno macehualli, tlahpiyalli zo tecuani oquichtli tlen huiyontoc imetztzalan; zan tolontic quence itecciz piyo. “Ce totlayi tlen ehua Alaxtitla temoc itecziz huan naman micqui.”
IDIEZ def. español: 
# 1. Una cosa redonda que se caí cuando pone una gallina; tiene su cáscara blanca, su clara es blanca y la yema es amarilla. “Mi hijo lo mandé que vaya a comprar huevo cuando ya se regresaba se cayó y los quebró”. 2. no. Una parte de las pompas de una persona y un animal silvestre macho que se encuentra debajo de las piernas; están redondos como el huevo de la gallina y no están muy grandes. “Un hombre alaxtecoh se le bajó los huevos y ahora se murió”.
IDIEZ gramática: 
tlat.