A lady (often quite large,) that prefers the (very) close company of other ladies, known as femmes. Regularly seen wearing a lumberjack shirt, boots and dungarees/bib & braces overalls.
Origin: Due to the normal extreme mass of these 'ladies,' it has often been assumed that locomotion could only be facilitated with the assistance of a powerful Diesel engine.
Source: Cutaway, Aug 9, 2004 "Dieseldyke" Urban Dictionary
Example: Said at the A&E Dept, "I hope you've learnt from that young man, never get between that Diesel and her Femme !"