# radioactive

/ˌɹeɪdioʊˈæktɪv/ (US) · /ɹˌeɪdɪəʊˈæktɪv/ (UK)

Source: https://englishreference.com/word/radioactive
Updated: 2026-06-20

## Senses

### 1. emitting radiation

adjective · CEFR B2 · Technical

sending out energy in the form of rays or particles that can be harmful to living things.

For teachers: exhibiting radioactivity through the spontaneous emission of ionising radiation from unstable atomic nuclei.

- The workers wore special suits to protect themselves from the radioactive waste.
- The containment vessel was designed to withstand the intense heat and pressure generated by the radioactive decay of the spent fuel rods.

Usage: Usually precedes the noun it modifies.

### 2. dangerous or toxic

adjective · CEFR C1 · Informal

so controversial, dangerous, or unpleasant that people want to avoid it completely.

For teachers: highly controversial or socially toxic; used figuratively to describe individuals or topics that are perceived as damaging to associate with.

- After the scandal, the politician became radioactive and no one wanted to work with him.
- The proposed policy became politically radioactive after the leaked documents revealed the true cost to the taxpayers.

Teaching tip: This is a common metaphorical use in business and politics to describe someone whose reputation is ruined.

## Examples

- The workers wear special suits to handle radioactive waste.
- Scientists used a Geiger counter to detect if the soil samples were radioactive after the industrial accident.
- The disposal of radioactive isotopes requires specialized containment facilities designed to withstand geological shifts over thousands of years while preventing environmental contamination.

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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.