Synonyms and related words :
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, impervious to, inaccessible, indurated, inflexible, insensitive, inured, leakproof, lost to, noiseproof, nonpuncturable, obstinate, out of reach, pachydermatous, proof, proof against, punctureproof, resistant, rustproof, shatterproof, shellproof, soundproof, steeled against, steely, stony, thick-skinned, tight, un-come-at-able, unaccessible, unamenable, unapproachable, unattainable, unavailable, undiscoverable, ungettable, unimpressionable, uninfluenceable, unmovable, unobtainable, unpassable, unperforable, unpersuadable, unpierceable, unpliable, unprocurable, unreachable, unreceptive, unresponsive, unsecurable, unsuggestible, unsusceptible, unswayable, unyielding, watertight, weatherproof