iron-hearted

adj 0.822

bulletproof

adj 0.740

bombproof

adj 0.693

ironbound

adj 0.682

iron

adj 0.678

adamantine

adj 0.671

armored

adj 0.663

impregnable

adj 0.651

fireproof

adj 0.645

hard-and-fast

adj 0.633

unassailable

adj 0.630

armoured

adj 0.629

hardened

adj 0.624

unbreakable

adj 0.623

invincible

adj 0.619

unshakable

adj 0.619

rock-ribbed

adj 0.617

cast iron

adj 0.617

brassbound

adj 0.616

stalwart

adj 0.614

invulnerable

adj 0.613

hard-set

adj 0.612

unflinching

adj 0.606

hard as nails

adj 0.605

rock hard

adj 0.604

inviolable

adj 0.602

watertight

adj 0.598

rustproof

adj 0.597

infrangible

adj 0.596

staunch

adj 0.596

stone cold

adj 0.594

indestructible

adj 0.594

olid

adj 0.593

indurate

adj 0.591

diehard

adj 0.590

indurated

adj 0.589

copper-bottomed

adj 0.589

steel

adj 0.588

sure-fire

adj 0.588

set in stone

adj 0.585

adamant

adj 0.583

airtight

adj 0.579

sturdy

adj 0.576

steadfast

adj 0.576

unwavering

adj 0.574

rigid

adj 0.573

resolute

adj 0.573

irrefutable

adj 0.572

undefeatable

adj 0.571

unswerving

adj 0.570

iron gray

adj 0.570

indefeasible

adj 0.568

indomitable

adj 0.566

hard-nosed

adj 0.565

solid

adj 0.565

unquestionable

adj 0.563

strong

adj 0.563

inexpugnable

adj 0.562

indubitable

adj 0.561

heatproof

adj 0.561

case hardened

adj 0.560

made of sterner stuff

adj 0.560

unyielding

adj 0.560

stainless

adj 0.559

infallible

adj 0.557

incontestable

adj 0.557

impervious

adj 0.557

unarmored

adj 0.556

steely

adj 0.556

apodictic

adj 0.555

rockbound

adj 0.554

concrete

adj 0.554

fortresslike

adj 0.554

unimpeachable

adj 0.554

industrial strength

adj 0.552

unbroken

adj 0.552

unbending

adj 0.552

uncompromising

adj 0.552

dead set

adj 0.551

inviolate

adj 0.550

cataphract

adj 0.549

stone deaf

adj 0.549

guaranteed

adj 0.549

tamperproof

adj 0.548

fire brick

adj 0.548

shatterproof

adj 0.548

hardy

adj 0.547

immune

adj 0.547

hard-boiled

adj 0.547

stainless steel

adj 0.546

secure

adj 0.546

inexorable

adj 0.545

absolute

adj 0.545

unsinkable

adj 0.544

shockproof

adj 0.544

hardline

adj 0.543

immutable

adj 0.542

unarguable

adj 0.542

incontrovertible

adj 0.542

weatherproof

adj 0.541