solid as a rock

adj — 2 senses

solid as a rock

adj

1

Extremely thick and heavy, so as to make it impossible to move.

We're not going to be able to break down this door: it's solid as a rock.

2

Of a person Very reliable and dependable

Stewart has been solid as a rock ever since becoming the new vice-chairman.

Synonyms: rock solid

Entry derived from the Wiktionary, under licence CC BY-SA 4.0 — list of authors.