1. Incapable of being overcome, challenged or refuted
   - impregnable

See also: unconquerable

• digress
• digression
• digressive
• digs
• dihedral
• dihybrid
• dihybrid cross
• dihydric alcohol
• dihydrostreptomycin
• dihydroxyphenylalanine
• Dijon
• dik-dik
• dika
• dika bread
• dika nut
• dike
• diktat
• Dilantin
• dilapidate
• dilapidated
• dilapidation
• dilatable
• dilatation
• dilatation and curettage
• dilate