# firm up

CEFR B2 · Phrasal verb

Source: https://englishreference.com/word/firm-up
Updated: 2026-10-22

## Definition

to make a plan or an arrangement more certain and final. You can also use it to describe making your body stronger or more solid.

For teachers: to make something more definite, stable, or certain. Often used transitively with abstract nouns like 'plans' or 'arrangements', or in a physical sense regarding muscle tone.

## Examples

- We need to firm up the details for our trip.
- After weeks of vague discussions, the two companies finally met to firm up the terms of the merger.
- The administration sought to firm up its policy on carbon emissions before the international summit commenced in late October.

## Pitfalls

- Not "We need to firm the plan." but "We need to firm up the plan." — The particle 'up' is required to change the adjective 'firm' into a phrasal verb meaning to make something definite.

## Usage notes

- This phrase is commonly followed by nouns like 'plans', 'details', or 'arrangements'.
- Teaching tip: Contrast with 'solidify' or 'finalize' to show how 'firm up' bridges the gap between casual and professional speech.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.