Principal English Translation: 

to enjoy; to be rich; to prosper; to enrich someone else; to make someone prosper; to please someone; in modern Eastern Huastecan Nahuatl, this means to teach

Orthographic Variants: 
Alonso de Molina: 

tlamachtia. nicno. (pret. onicnotlamachti.) gozar o fruir de algo.
tlamachtia. nino. (pret. onitlamachti.) ser rico de hazienda, o gozarse mucho.
tlamachtia. nite. (pret. onitetlamachti.) enriquecer a otro, hazerlo prospero.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, f. 125r.

Frances Karttunen: 

TLAMACHTIĀ vrefl, vt to be rich, to enjoy oneself; to enrich someone, to make someone prosperous / ser rico de hacienda o gozarse mucho (M), enriquecer a otro y hacerlo prospero (M) M has this as a double object verb, taking a reflexive prefix and an object prefix, with the sense ‘to enjoy something, to take pleasure in something.’ This is homophonous with TLAMACHTIĀ < MACHTIĀ ‘to teach something.’ See TLAMACH.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 278–279.

Lockhart’s Nahuatl as Written: 

(1) nic. to enjoy something. Class 3: ōnictlamachtih.
(2) nino. to be wealthy; to be happy.

James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 237.

Attestations from sources in English: 

nican, otomotlamachti otomocuiltono = here you have become rich, you have become wealthy (central Mexico, sixteenth century)
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 237.

teyollali, tepaquilti, tecuiltono, tetlamachti = he makes people happy, satisfied (Juan Bautista, ca. 1599, Mexico City)
Susanne Klaus, Uprooted Christianity: The Preaching of the Christian Doctrine in Mexico, Based on Franciscan Sermons of the 16th Century Written in Nahuatl (Bonn: Bonner Amerikanistische Studien e. V. c/o Seminar für Völkerkunde, Universität Bonn, 1999), 247.

Tlazcamati hueyi tlamachtiani. = Thank you, great teacher. (modern Nahuatl
Victoriano de la Cruz Cruz, Facebook posting, June 5, 2014, Nahuatlahtolli page. Translated to English by Stephanie Wood.