adjective
- utterly unyielding or firm in attitude or opinion.
- too hard to cut, break, or pierce.
- like a diamond in luster.
adjective
- very hard; unbreakable or unyielding
- having the lustre of a diamond
c.1200, from Latin adamantinus “hard as steel, inflexible,” from Greek adamantinos, from adamas (see adamant (n.)).