Webster’s 1913 has no entry under this spelling.
Shades of meaning
Fernald has no entry of its own for unyielding; he lists it under obstinate, severe.
Where he writes about it:
The unyielding conduct which we approve we call decided, firm, inflexible, resolute; that which we condemn we are apt to term headstrong, obstinate, stubborn. — from obstinate
Synonyms
obstinatesevereausterecontumaciousdecideddetermineddoggedfirmfixedhardharshheadstrongheadyimmovableindomitableinexorableinflexibleintractablemorosemulishobdurateopinionatedpersistentpertinaciousrefractoryrelentlessresoluteresolvedrigidrigoroussternstiffstrictstubbornuncompromisingunconquerableunflinchingunmitigatedunrelenting