inflexible
backed
bone
bony
calcified
callous
calloused
case-hardened
crusted
crusty
crystallized
deep-seated
démodé
established
fixed
fossilized
granulated
hard-and-fast
hardened
hornified
incrusted
indurate
indurated
ingrained
lapidified
old-fashioned
osseous
ossicular
ossiferous
osteal
out of date
outdated
outmoded
passé
petrified
reinforced
rigid
rigidified
sclerotic
set
solidified
steeled
stiffened
strengthened
toughened
vitrified