Principal English Translation:
a sailor; a bad person (see Molina and attestations)
Lockhart’s Nahuatl as Written:
natlacatl = I am a bad person, I am inhumane
This is an example of the way i gives way before any following vowel (in this case, a, the first letter of atlacatl). If it didn't give way, the word would be niatlacatl.
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), 2.
Attestations from sources in English:
The Matrícula de Huexotzinco includes a person named Felipe Amin who has an occupation listed as Tlatlama Atlacatl, which suggests that he is fishes perhaps from a boat. Thus, this atlacatl would be more akin to the translation as "sailor." (See f. 576r.)
Notes from Stephanie Wood. See the forthcoming entry in her Visual Lexicon of Aztec Hieroglyphs.)
a bad or inhuman person, monster. ah negative, tlacatl.
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), 211.