Definition of "secondman"

The secondman looks back from 'Slim Jim' Class 33 No. 33211 as it trundles through Gravesend station with a permanent way train in 1977. The first wagon's sides are literally bulging at the seams with ballast spoil.

2018, Andy Gibbs, The Southern Region in the 1970s and 1980s, Amberley Publishing page 12, photo caption

And instead of carrying commuters, the only people on many evening trains between Hatfield and St Albans were the driver and secondman.

2023 March 8, Howard Johnston, “Was Marples the real railway wrecker?”, in RAIL, page 50