Opinionated, a.
Stiff in opinion; firmly or unduly adhering to one's own opinion or to preconceived notions; obstinate in opinion. Sir W. Scott.
Shades of meaning
Fernald has no entry of its own for opinionated; he lists it under dogmatic, obstinate.
He lists it without comment; the entries above explain its neighbors.
Synonyms
dogmaticobstinatearrogantauthoritativecontumaciousdecideddetermineddictatorialdoctrinaldoggeddomineeringfirmfixedheadstrongheadyimmovableimperiousindomitableinflexibleintractablemagisterialmulishobdurateoverbearingpersistentpertinaciouspositiverefractoryresoluteresolvedself-opinionatedstubbornsystematicunconquerableunflinchingunyielding