The word "infixed" commonly refers to something that is firmly planted or deeply embedded. Some synonyms for this word include ingrained, implanted, rooted, lodged, and fixed. These words all convey a sense of something being firmly established or deeply rooted, often in a way that is difficult to dislodge or remove. Other similar words include entrenched, established, solidified, and fortified, which also suggest a degree of strength, stability, and durability. Whether describing an idea, a habit, or a physical object, these words all suggest a sense of permanence and steadfastness.