the water (e.g., the sea) that connects with the sky; the sky is like a house, and the water is like walls; ilhuicaatl is a synonym of teoatl (see attestations)
the celestial realm, heaven, sky (see also ilhuicac); another definition for ilhuicatl is a wooden bearing wall or a beam that carries the superstructure of a house, in construction terminology [see the Digital Florentine Codex Book 11, f 119v., at https://florentinecodex.getty.edu/book/11/folio/119v?spTexts=&nhTexts=]