Synonyms of hard-and-fast

hard-and-fast

adjective

ˌhärd-ᵊn-ˈfast 

1

as in certain

having been established and usually not subject to change

hard-and-fast rules that governed the corporate environment in those days included strictures regarding office dress that were rigidly enforced

Synonyms & Similar Words

• certain
• stable
• final
• unchanging
• unchangeable
• fixed
• hard
• determinate
• firm
• set
• flat
• specific
• steady
• definite
• inexpugnable
• constant
• frozen
• settled
• explicit
• uniform
• exact
• good
• nonnegotiable
• reliable
• stipulated
• solid
• true
• dependable
• sure
• safe
• unwavering
• nonadjustable
• stated
• responsible
• noncancelable
• trustworthy
• tried-and-true
• given
• trusty
• tried

Antonyms & Near Antonyms

• negotiable
• adjustable
• changeable
• indefinite
• unspecified
• uncertain
• variable
• unpredictable
• capricious
• volatile
• fluid
• open-ended
• mutable
• unstable
• mercurial
• unsteady
• inconstant
• temperamental
• fluctuating
• unsettled
• changeful
• flickery

2

as in unchangeable

not capable of changing or being changed

hard-and-fast beliefs that are the rock-solid foundation of their religion

Synonyms & Similar Words

• unchangeable
• unchanging
• fixed
• invariable
• unalterable
• determinate
• immutable
• inflexible
• inalterable
• steadfast
• constant
• established
• steady
• unvarying
• incommutable
• stable
• changeless
• unaltered
• set
• immovable
• settled
• unmovable

Antonyms & Near Antonyms

• variable
• flexible
• elastic
• changeable
• adaptable
• uncertain
• adjustable
• mutable
• varying
• unstable
• fickle
• alterable
• plastic
• unsettled
• pliable
• inconstant
• fluctuating
• willowy
• supple
• pliant

Example Sentences

Recent Examples of hard-and-fast

There are no hard-and-fast rules on how to log a home run or whether a circus catch ought to be recorded as more than an out. — Jacob Feldman, Sportico.com, 24 Apr. 2026

Dogs bred for alertness or reactivity may be more attuned to sound, though this isn’t a hard-and-fast rule. — Jamie Cuccinelli, Martha Stewart, 7 Apr. 2026

There are no hard-and-fast rules for replacing a mattress. — Sharon Brandwein, USA Today, 3 Apr. 2026

One hard-and-fast rule to live by in this case? — Stacia Datskovska, Footwear News, 26 Jan. 2026