# alum

/ˈæɫəm/ (US)

Source: https://englishreference.com/word/alum
Updated: 2026-08-27

## Senses

### 1. former student

noun · CEFR B2 · American English · Informal

a person who used to attend or graduated from a specific school or university.

For teachers: an informal clipping of alumnus or alumna, referring to a former student or graduate of an educational institution.

- As a famous alum of this college, she was invited to give a speech.
- The university's annual fundraising gala relies heavily on the generosity of its successful alums who wish to give back to their departments.

Usage: Commonly used as a gender-neutral singular or plural form in casual contexts.

### 2. chemical salt

noun · CEFR C1 · Technical

a white mineral salt used in things like medicine, dyeing cloth, or making pickles.

For teachers: a specific double sulphate of potassium and aluminium, or a similar compound, used as an astringent or mordant.

- The recipe for these crispy pickles calls for a small amount of alum.
- In traditional dyeing processes, alum is frequently employed as a mordant to help the pigment bond permanently with the fabric fibres.

Usage: Uncountable when referring to the substance generally; countable when referring to specific chemical varieties.

### 3. to treat with chemicals

verb · CEFR C2 · Technical

to treat something with alum, usually to prepare it for dyeing or tanning.

For teachers: to steep in or impregnate a material with a solution of alum.

- The leather was alumed to prepare it for the tanning process.
- The textile conservator carefully alumed the silk samples to ensure the new dyes would take evenly across the historical reconstruction.

Usage: A transitive verb primarily used in industrial or historical chemistry contexts.

## Examples

- She is a proud alum of the local state university.
- The university invited a successful alum to give a speech at the graduation ceremony.

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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.