rock solid

adj — 2 senses

rock solid

adj
1

Physically very solid; very difficult to move.

2

Figuratively Very strong and dependable.

  • Wolfgang Schäuble said on Tuesday he had “no concerns” about Deutsche Bank, speaking shortly after John Cryan, who was appointed to run Germany’s biggest bank seven months ago, sent an email to his 100,000 staff to assure them the bank was “absolutely rock solid”.2016 February 9, Jill Treanor, quoting John Cryan, “Deutsche boss tells staff the bank is ‘rock solid’ as shares slide”, in The Guardian:
Synonyms
rock hard, solid as a rock

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