acid-fast
colorfast
corrosion-resistant
fast
greaseproof
ladder-proof
moth-resistant
mothproof
proof
resistant
rot-resistant
run-resistant
runproof
soundproof
Philistine
airtight
ballproof
beyond reach
bombproof
bulletproof
burglarproof
callous
calloused
case-hardened
closed forever to
closed to
corrosionproof
dampproof
fire-resisting
fireproof
flameproof
flinty
foolproof
hard
hardened
hardhearted
hermetic
holeproof
impassable
impenetrable
impermeable
impersuadable
impersuasible
imperviable
impervious to
inaccessible
indurated
inflexible
insensitive
inured
leakproof
lost to
noiseproof
nonpuncturable
obstinate
out of reach
pachydermatous
pathless
proof against
punctureproof
imperviously
imperviousness
defenseless
impregnable
indestructible
innocuous
insensible
insurmountable
intact
invulnerable
nonexistent
oblivious
unable
unafraid
unassailable
unconcerned
uneventful
uninhabitable
uninhabited
unscathed
valueless