Adjective
(simile) Extremely stable physically.
(simile) Extremely reliable.
Source: en.wiktionary.orgI could have been a sailor, could have been a cook, A real live lover, could have been a book, I could have been a signpost, could have been a clock, As simple as a kettle, steady as a rock. I could be here and now, I would be, I should be, but how? I could have been one of these things first. Nick Drake