WordNet sense 1 (unreasonably rigid in the face of argument or entreaty or attack):

mulish

WordNet sense 2 (tenaciously unwilling or marked by tenacious unwillingness to yield):

obstinate, stubborn, unregenerate

WordNet sense 3 (guided by practical experience and observation rather than theory):

hard-nosed, practical, pragmatic

WordNet sense 4 (aware or expressing awareness of things as they really are):

realistic