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

See also: unconquerable

• phat
• phatic communication
• phatic speech
• PhD
• pheasant
• pheasant coucal
• pheasant cuckoo
• pheasant under glass
• pheasant's-eye
• Phegopteris
• Phegopteris connectilis
• Phegopteris hexagonoptera
• Pheidias
• phellem
• Phellodendron
• Phellodendron amurense
• phenacetin
• phenacomys
• phenanthrene
• Phenaphen
• phenazopyridine
• phencyclidine
• phencyclidine hydrochloride
• phenelzine
• Phenergan