Definition of "dingy"

The station has been refurbished both at ground level and below ground, where the wide, fluorescently lit platforms are an almost unrecognisable metamorphosis of the dingy, reeking Low Level of old.

1960 December, “The Glasgow Suburban Electrification is opened”, in Trains Illustrated, page 713

He led her at last into a dingy sanctum, dimly lighted by one shaded lamp. In this safe there were piles of dingy papers and more dingy ledgers ; with great piles of accounts on hooks in the wall

1854, Charles Dickens, Household Words

She's looking from Tarquin to Fenella with shining eyes, and I look at the picture interestedly over her shoulder. But to be honest, I can't say I'm impressed. For a start it's really dingy – all sludgy greens and brown

2009, Sophie Kinsella, The Secret Dreamworld Of A Shopaholic: (Shopaholic Book 1)