Synonyms of cast-iron

cast-iron

adjective

ˈkast-ˈī(-ə)rn 

1

as in strict

not allowing for any exceptions or loosening of standards

lost weight only after a cast-iron adherence to his diet

Synonyms & Similar Words

• strict
• rigorous
• rigid
• stringent
• steadfast
• uncompromising
• exacting
• inflexible
• hard-line
• adamant
• conscientious
• meticulous
• undeviating
• brassbound
• stubborn
• unbending
• punctilious
• exact
• adamantine
• scrupulous
• relentless
• immovable
• painstaking
• unflinching
• tenacious
• firm
• close
• implacable
• unyielding
• hardened
• fussy
• dogged
• stern
• tough
• unrelenting
• flinty
• resolved
• determined
• ironbound
• single-minded
• severe
• harsh
• unsparing
• grim
• hard
• demanding
• austere
• unappeasable
• hard-hearted

Antonyms & Near Antonyms

• flexible
• loose
• lax
• slack
• pliant
• compliant
• relaxed
• pliable
• yielding
• soft
• mild
• acquiescent
• gentle
• easy
• indulgent
• tolerant
• lenient
• merciful
• kindly
• easygoing
• compromising
• sloppy
• slipshod
• negligent
• slovenly
• remiss
• relenting
• neglectful
• unfussy
• spoiling
• pampering

2

as in sturdy

able to withstand hardship, strain, or exposure

he has a cast-iron faith in his innate ability to overcome any adversity that life might throw against him

Synonyms & Similar Words

• sturdy
• hardy
• strong
• stout
• rugged
• hardened
• tough
• vigorous
• durable
• robust
• permanent
• healthy
• toughened
• hard
• staunch
• hard-bitten
• leathery
• resilient
• stable
• flinty
• enduring
• stalwart
• muscular
• inured
• thriving
• lasting
• unyielding
• everlasting
• immortal
• tenacious
• imperishable
• fortified
• brawny
• staying
• flourishing
• tempered
• virile
• hale
• sound
• seasoned
• husky
• fit
• lusty
• able-bodied
• annealed
• strapping
• prospering
• red-blooded

Antonyms & Near Antonyms

• weak
• soft
• delicate
• tender
• worn
• diseased
• wasted
• weakened
• enfeebled
• unsound
• fragile
• emasculated
• infirm
• exhausted
• frail
• puny
• nonhardy
• crippled
• temporary
• incapacitated
• debilitated
• sensitive
• worn-out
• susceptible
• vulnerable
• run-down
• yielding
• transient
• enervated
• sapped
• mortal
• resistless
• perishable
• unresistant

Example Sentences

Recent Examples of cast-iron

Engineer James Mansergh created the neo-Byzantine tower, topping it with a 32,000-gallon cast-iron tank to hold and supply clean water. — Bailey Bujnosek, InStyle, 19 Aug. 2026

Today, the town’s Victorian grandeur is rotting and crumbling away, its cast-iron piers corroded by sea salt. — George Francis Lee, New Yorker, 12 Aug. 2026

Its interior design matches the vibe, with elegant period-style design complemented by touches of country life—riding boots placed beside a cast-iron fireguard inside, terracotta pots next to Victorian wrought-iron chairs on the outdoor patio. — Katie Silcox, Vogue, 6 Aug. 2026

Workers pack the fuel rods inside cast-iron structural inserts, which sit within thick copper outer canisters. — Aman Tripathi, Interesting Engineering, 5 Aug. 2026