Definition of "slummy"

Cars and unemployment increased. Council houses took on a slummier look.

2003, Alasdair Gray, “Miss Kincaid's Autumn”, in Every Short Story, Canongate, published 2012, page 745

The dreamer is a distinguished operatic artist, and, like all who have elected to follow, not the safely marked general highways of the day, but the adventure of the special, dimly audible call that comes to those whose ears are open within as well as without, she has had to make her way alone, through difficulties not commonly encountered, "through slummy, muddy streets"; she has known the dark night of the soul, Dante's "dark wood, midway in the journey of our life," and the sorrows of the pits of hell[.]

1968, Joseph Campbell, The Hero with a Thousand Faces, 2nd edition, London: Fontana Press, published 1993, page 21