Green’s Dictionary of Slang

diesel n.

[SE diesel, a locomotive driven by a diesel engine]

1. (UK prison) prison tea [its taste, supposedly reminiscent of diesel fuel].

[UK]Guardian G2 11 Feb. 4: ‘Tea’ – actually a greasy, tobacco tinctured liquid served lukewarm from buckets and affectionately known as ‘diesel’.
[UK]N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 128: Two slices of bread, a pat of marg and a cup of diesel.
[UK]J.J. Connolly Viva La Madness 73: A gallon of strong diesel tea made with long-life milk.

2. (US) one who has a muscular, well-developed physique.

[US]C. Hiaasen Double Whammy (1990) 33: It was only when he got to his feet that Decker saw what a diesel he truly was.
[US]Hope College ‘Dict. of New Terms’ [Internet] diesel n. Someone who is strong, muscular, or buff.

3. see diesel-dyke n.

In compounds

SE in slang uses

In compounds

diesel therapy (n.) [the diesel engine of the bus that transports the prisoners; the circuit of prisons around which they are taken]

(US prison) the constant movement of an inmate between prisons.

[US]Other Side of the Wall: Prisoner’s Dict. July [Internet] Diesel Therapy: Constant transfers [between prisons] to keep a prisoner from associating with others or to discourage particular activity.

In phrases