# sludge

/ˈsɫədʒ/ (US) · /slˈʌdʒ/ (UK)

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

## Senses

### 1. thick mud or waste

noun · CEFR B2

a thick, wet, and messy mixture of liquid and solid material, like mud or waste.

For teachers: a thick, semi-solid mixture of liquid and solid components, typically associated with industrial waste, sewage, or heavy mud.

- The heavy rain turned the garden path into a mess of thick, black sludge.
- Environmental inspectors discovered that the factory had been illegally dumping toxic sludge into the local river system for years.

### 2. administrative friction

noun · CEFR C1 · Academic · Technical

annoying rules or paperwork that make it difficult and slow to get things done.

For teachers: institutional policies or bureaucratic hurdles that introduce unnecessary tedium and inefficiency into a process.

- The new government website was full of sludge that made applying for a passport very difficult.
- Economists argue that administrative sludge in the healthcare system costs the country billions in lost productivity every year.

Usage: Often used in behavioral economics to describe the opposite of a 'nudge'.

### 3. music genre

noun · CEFR C1 · Informal

a style of heavy metal music that is very slow, loud, and dark.

For teachers: a subgenre of heavy metal music, characterized by slow tempos, abrasive rhythms, and a pessimistic atmosphere.

- He spent the evening listening to old sludge records in his room.
- The band's latest album is a masterclass in sludge, blending doom metal influences with a raw, aggressive production style.

### 4. to move or sit heavily

verb · CEFR C2 · Informal · Dialect

to sit or move in a heavy, lazy way.

For teachers: to slump, slouch, or move with a heavy, lethargic gait.

- After the long hike, he just sludged down into the armchair and fell asleep.
- The exhausted commuters sludged toward the train platform, their heads bowed against the biting winter wind.

## Examples

- The workers had to clear the thick sludge from the pipes.
- After the heavy rains, a layer of dark sludge covered the bottom of the garden path.
- Environmental inspectors discovered that the factory had been illegally dumping toxic sludge into the local river system for several months.

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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.