backside

backside — noun

1. the rounded fleshy area on a person, made up of two cheeks, that takes your weig

1.nounB1
Definition

the rounded fleshy area on a person, made up of two cheeks, that takes your weight when you sit down; a casual, slightly humorous word for the buttocks.

Example

Xiomara slipped on the icy step and landed flat on his backside.

collocation: land / fall on one's backside

Aunt Linda swatted the puppy lightly on its backside for chewing the rug.

Common collocations
  • land on one's backside
  • fall on one's backside
  • kick someone's backside
  • smack on the backside
Synonyms
  • buttocks

    neutral, anatomical term suitable in any register

  • bottom

    everyday, mild, common in British family speech

  • behind

    polite informal, often used around children

  • butt

    very informal, more common in American English

Grammar Patterns

on + one's + backside

Usage Note

Slightly softer and more polite than 'arse' or 'butt', but still informal — avoid in formal writing or polite company. Often used humorously, especially after a fall or a long sit.

Common Mistakes

The doctor examined my backside.' (in a clinical setting).
The doctor examined my buttocks.
use the neutral medical term in formal or clinical contexts; 'backside' sounds too casual.

2. the rear surface or side of a thing — the part facing away from the viewer, oppo

2.nounB2
Definition

the rear surface or side of a thing — the part facing away from the viewer, opposite to the front you normally look at or use.

Example

Kalani taped her phone number to the backside of the bookshelf so guests would not see it.

the backside of + concrete object

There is a small loading door on the backside of the warehouse, near the parking lot.

Common collocations
  • the backside of the building
  • the backside of the shelf
  • on the backside
Synonyms
  • back

    the most natural choice for documents, buildings, and most objects

  • rear

    slightly more formal; common for vehicles and buildings

  • reverse

    used for coins, medals, pages, and printed sides

Antonyms
  • front

    the side you normally face or use

  • face

    for clocks, coins, and other display surfaces

Grammar Patterns

the backside of + noun

Usage Note

Sounds slightly informal in this spatial sense; many writers prefer 'back' or 'rear' for objects, and 'reverse' for coins, photos, and pages. Use 'backside' when you want a plain, conversational word.

Common Mistakes

Please sign the backside of the form.
Please sign the back of the form.
for paper documents, photos, and coins, English speakers say 'the back' or 'the reverse', not 'the backside'.
Idioms

a pain in the backside/arse

idiom

Someone or something that causes a lot of trouble or annoyance.

My little brother is a real pain in the backside when he's bored.

Filling out these tax forms is a pain in the backside every year.

backside — idiom

Word family

Synonym discussion

Sense: noun/1

All five words name the same body part, but they differ in tone and audience. 'Buttocks' is the neutral, anatomical term that doctors, nurses, and writers use without sounding crude. 'Bottom' is mild and family-friendly, very common in British homes when speaking to or about children. 'Behind' is a polite, slightly old-fashioned euphemism — handy when you want to avoid sounding crude. 'Backside' sits in the middle: informal, often slightly humorous, and frequently used after a tumble ('She landed on her backside.'). 'Butt' is the most casual of the group and feels especially American; you would hear it among friends but not in a hospital report. So a doctor might write 'pain in the buttocks', a parent might say 'wash your bottom', and a friend might laugh 'I fell flat on my backside.'

backside ↗buttocksbottom ↗behind ↗butt ↗

Etymology

Old EnglishMiddle EnglishModern English

Formed in Middle English from the everyday words 'back' and 'side', simply meaning 'the side at the back'. For centuries it just described the rear surface of any object. From the 16th century onwards, English speakers began using it as a polite, slightly playful way to refer to the human buttocks — preferring it to blunter, older words. Both meanings have lived side by side ever since, though the body-part sense is now far more common in everyday speech.