The Collaborative International Dictionary of English v.0.48:

hardheaded \hard"head`ed\, hard-headed \hard"-head`ed\, a.
   Having sound judgment; sagacious; shrewd; practical and
   pragmatic. -- Hard"-head`ed*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hardheaded
    adj 1: unreasonably rigid in the face of argument or entreaty or
           attack [syn: hardheaded, mulish]
    2: 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" [syn:
       hardheaded, hard-nosed, practical, pragmatic]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "hardheaded":
   balking, balky, bigoted, bulldogged, bulletheaded, bullheaded,
   case-hardened, dogged, dogmatic, down-to-earth, earthy, fanatic,
   hard, hard-boiled, headstrong, hoaxproof, intolerant,
   matter-of-fact, mulish, not born yesterday, obstinate, opinionated,
   overzealous, persevering, pertinacious, pigheaded, positivistic,
   practical, practical-minded, pragmatic, rational, realist,
   realistic, reasonable, restive, sane, scientific, scientistic,
   secular, self-willed, sensible, set, sober, sober-minded,
   sophisticated, sound, sound-thinking, stiff-necked,
   straight-thinking, strong-willed, strongheaded, stubborn, sulky,
   sullen, tenacious, tough-minded, uncooperative, uncullible,
   undeceivable, undeludable, undupable, unfoolable, ungullible,
   unhoaxable, unideal, unidealistic, unregenerate, unromantic,
   unseduceable, unsentimental, willful, wise, worldly