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• hard-and-fast
  hard-and-fast

  adjective

  strongly binding; not to be set aside or violated.
• hard and fast
  hard and fast

  adjective

  (hard-and-fast when prenominal) (esp of rules) invariable or strict

hard-and-fast

American  

[hahrd-n-fast, -fahst] / ˈhɑrd nˈfæst, -ˈfɑst /

adjective

1. strongly binding; not to be set aside or violated.

   hard-and-fast rules.

   Synonyms:

   unambiguous, rigorous, inviolable, inflexible, precise, fixed

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hard and fast British  

adjective

1. (hard-and-fast when prenominal) (esp of rules) invariable or strict

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hard and fast Idioms  

1. Defined, fixed, invariable, as in We have hard and fast rules for this procedure. This term originally was applied to a vessel that has come out of water, either by running aground or being put in dry dock, and is therefore unable to move. By the mid-1800s it was being used figuratively.

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Other Word Forms

• hard-and-fastness
  noun

Etymology

Origin of hard-and-fast

First recorded in 1865–70

Example Sentences

That’s not because the travel industry has a hard-and-fast rule about when to buy flights, but because the loosely understood best practice of a one-to-three-month advance window for nonholiday travel hasn’t arrived yet.

From Slate • May 12, 2026

There are no hard-and-fast rules about when a place name or other traditional description attached to a product becomes generic.

From The Wall Street Journal • Apr. 6, 2026

This is why the broadcast limit is not really a hard-and-fast limit.

From BBC • Mar. 30, 2026

I’m not necessarily sold on hard-and-fast rules when it comes to age; it also depends on your risk tolerance, expected longevity and how long you intend to work.

From MarketWatch • Dec. 11, 2025

While there are only ten hard-and-fast laws to the Scythedom, there are many accepted conventions.

From "Scythe" by Neal Shusterman