large pit, ravine, hole in the earth (see Molina and Karttunen), might also have referred to a type of soil (see attestations)
See an image that represents tlacomolli in the Visual Lexicon of Aztec Hieroglyphs, ed. Stephanie Wood (Eugene, Ore.: Wired Humanities, 2020-present).
tlacomule = level land soils in Alta, Puebla (twentieth century)
huel onpa tlantica yn canpa ca huey tlacomonli = llega hasta el hoyo grande (Tlatelolco, 1609)