1. Not easily solved
   "public finance...had long presented problems unsolvable or at least unsolved"
   - insolvable, unsoluble, unresolvable

See also: insoluble

• affection
• affectional
• affectionate
• affectionately
• affectionateness
• affective
• affective disorder
• affenpinscher
• afferent
• afferent fiber
• afferent nerve
• afferent neuron
• affiance
• affiant
• affidavit
• affiliate
• affiliated
• affiliation
• affinal
• affine
• affine geometry
• affine transformation
• affined
• affinity
• affirm