Scruffy means untidy and worn, as though nobody has bothered. Trainers gone grey at the toes, a jumper with a thread hanging off it, hair that has not met a comb this week.
It works on people, animals, clothes and places alike: a scruffy student, a scruffy little terrier, a scruffy end of town with weeds coming up through the pavement. Keep it apart from dirty, because scruffy is about neatness rather than dirt, and a shirt can be spotless and still scruffy. It is mild, and it can even be affectionate, since calling a dog scruffy is close to a compliment. The word people set against it is smart: 'wear the smart shoes, not those scruffy ones.' A person who looks that way is a scruff, and the whole family of words is far more British than American.
From scruff + -y.
Etymology from Wiktionary, CC BY-SA