Definition: (Adjective) Absolutely unyielding on some issue or principle and totally impervious to pleas or reasoning. (definitivamente contra, bater o pé)

Usage: An "adamant" is also a noun meaning a stone impenetrable in its hardness or any extremely hard substance. The adjective has an adverb "adamantly" and a noun "adamancy."

Suggested Usage: Are you failing to alienate your kids? Here is a good way to encourage them to leave home: "I am adamant that you will not see that tattooed idiot with the riveted ears and the motorcycle again!" (Seriously, be flexible and accommodative—accept the tattoos if the motorcycle goes.) "She adamantly refused to board the plane to Europe."
Source: YourDictionary