piece of junk; worn-out thing
Refers to a broken-down, useless object, often a machine or vehicle. Colloquial and slightly derogatory.
This computer is a piece of junk now.
This car has become a piece of junk now.
Describes a person or thing that is unreliable, incompetent, or not functioning properly. Often used in a self-deprecating or teasing way.
That player has been useless lately.
I'm really no good; I forget things right away.
dismantled car; scrapped vehicle
Specifically a car that has been taken apart for parts or scrap. A specialized use within the junk sense.
Let's take usable parts from this dismantled car.
Dated slang for a punch or hitting someone. Rarely used in modern Japanese.
Apparently old-time delinquents used to say things like 'give 'em a punch'.
When it comes to operating machines, I'm hopeless.
He keeps driving his beat-up old car with care.
役立たず bluntly means 'useless person/thing' with a harsher tone, whereas ポンコツ is softer and often used self-deprecatingly or teasingly.
Katakana spelling is standard for this colloquial term.
Hiragana spelling is also used, especially in casual writing.
The exact origin is uncertain. It may be related to the sound of something breaking or being struck, but there is no clear historical derivation.