I. -lē, -li adjective
Etymology: slattern (I) + -ly (adjective suffix)
1. : untidy and usually dirty through habitual neglect : slovenly , unkempt
tatterdemalion, slatternly , slipshod women — E.C.Clayton
streets terribly shabby and slatternly and badly paved — Arnold Bennett
also : careless , disorderly
I am … slatternly ; I seldom put, and never keep things in order; I am careless — Charlotte Brontë
2. : of, relating to, or characteristic of a slut or harlot
Synonyms:
dowdy , frowsy , blowsy : slatternly stresses notions of slovenliness, unkemptness, and sordidness
a small, slatternly looking craft, her hull and spars a dingy black, rigging all slack and bleached nearly white, and every thing denoting an ill state of affairs aboard — Herman Melville
lived with them, in the slatternly apartment among the unwashed dishes in the sink and on the table, the odor of stale tobacco smoke, the dirty shirts and underwear piled in corners — R.P.Warren
dowdy may apply to a complete lack of taste typically marked by a blend of the untidy, unfit, or either drab or tawdry
her shoes were bought a long time ago and have no relation to the dress, and the belt of her dress has become untied and is hanging down. She looks clean and dowdy — Lillian Hellman
so dreadfully dowdy that she reminded one of a badly bound hymnbook — Oscar Wilde
frowsy suggests a lazy lack of neatness, order, and cleanliness
a dumpy, frowsy woman, clad in old dress and apron — A.J.Coutts
if a fully fed, presentably clothed, decently housed, fairly literate and cultivated and gently mannered family is not better than a half-starved, ragged, frowsy, overcrowded one, there is no meaning in words — G.B.Shaw
blowsy suggests rude, loud, florid coarseness and lack of refinement
a big blowsy Jezebel from the docks — Bruce Marshall
the fat and blowsy wife bowed in an exaggerated fashion, never stopping the while to fan her red face vigorously — Louis Bromfield
II. adverb
Etymology: slattern (I) + -ly (adverb suffix)
: in a slatternly manner