1.
You describe someone as ~ when they have very strong, fixed ideas about something and are unlikely to change their mind. (WRITTEN)
The authorities proved ~ on one crucial opposition demand...
His ~ attitude on this subject was that since he had done it, so could everyone.
ADJ
2.
If a barrier or surface is ~, it is very solid or hard. (LITERARY)
...the troopers, who had to build roads through those ~ mountains...
He sat on the edge of an ~ armchair, a cup of tea in his hand.
ADJ