1) Mulish 2) Realistic 3) Stubborn 1) Mulish 2) Shrewd, practical 3) Stubborn 4) Tough, shrewd 
[adj] - unreasonably rigid in the face of argument or entreaty or attack 2. [adj] - guided by practical experience and observation rather than theory
hard-nosed adjective guided by practical experience and observation rather than theory; `a hardheaded appraisal of our position`; `a hard-nosed labor leader`; `completely practical in his approach to business`; `not ideology but pragmatic politics`