1. Deeply and firmly rooted, ingrained, or established. Hyphenated if used as a modifier. His bred-in-the-bone etiquette came as a result of his years of military training. In this part of the country, hospitality is simply bred in the bone.

2. Long-standing and habitual, especially of ideology or religion. Hyphenated if used as a modifier. Most people vote according to their bred-in-the-bone political identification, rather than making individual assessments of different candidates. A lot of times, religious views are simply bred in the bone.