We found one dictionary that defines the word as solid as a rock:

General (1 matching dictionary)

1. as solid as a rock: Merriam-Webster

▸ Words similar to as solid as a rock ▸ Usage examples for as solid as a rock ▸ Idioms related to as solid as a rock ▸ Wikipedia articles (New!) ▸ Words that often appear near as solid as a rock ▸ Rhymes of as solid as a rock ▸ Invented words related to as solid as a rock