An adjective for the condition of a used brush
What adjective best describes the weariness and disarrangement that starts to show in your toothbrush when you've used it for some time? Nothing severe; just a little out of shape:
It doesn't have to be exclusively applicable to brushes.
Solution 1:
frayed:
(of cloth) with threads in it that are starting to come apart
(Oxford Advanced Learner's Dictionary)
"It is not very good for your teeth once the bristles are bent or frayed in any direction."
("How to Reuse Old Toothbrushes" at WikiHow)
Google image search for: frayed toothbrush
Note: This adjective seems to be more commonly applied to the bristles than to the brush itself. For example, the image in the question could be called "an old toothbrush with frayed bristles."
Another more general adjective that people often use to describe brushes like these is worn (or worn out, worn down):
(of a thing) damaged or thinner than normal because it is old and has been used a lot
(Oxford Advanced Learner's Dictionary)
A worn-down and frayed toothbrush can't clean your teeth as well.
("Tooth Brushing Techniques For Whiter Teeth," by Rebecca Desfosse, from the "Colgate Oral Care Center")
Lastly, a term I used while researching this question: old. With something like a toothbrush that deteriorates over time, the adjective old generally implies lower quality. This connotation is less strong for some other things such as wine that are considered to improve with age.
Solution 2:
I would call that toothbrush 'frazzled', or 'frazzled out', depending on how much of a colloquial tone I wanted--'frazzled out' being the more colloquial.
'Frazzled' is the adjective formed from the past participle of 'to frazzle':
fraz·zle (frăz′əl) Informal
v. fraz·zled, fraz·zling, fraz·zles
v.tr.
1. To wear away along the edges; fray.
[American Heritage® Dictionary of the English Language, Fifth Edition. S.v. "frazzled." Retrieved February 5 2016 from http://www.thefreedictionary.com/frazzled ]
American Heritage offers this speculation about the origins of 'frazzle':
[Perhaps a blend of fray and dialectal fazzle, to unravel (from Middle English facelyn, to fray, from fasel, frayed edge, probably diminutive of fas, rootlets, from Old English fæs).]
(op. cit.)
Here are some contemporary examples of the term in use:
On the counter was his frazzled toothbrush, while the soap had slipped into the sink.
(From "Welcoming Death", by Jake Teeny, in the January/February 2016 issue of The Saturday Evening Post. Emphasis mine.)
In order to earn pocket money, the girl has spent many past summers hunched over the bathtub with a frazzled toothbrush.
(From "Dead Hens for Broken Eggs", by Sara Baume, published Mon., Dec. 28, 2015, in The Irish Times. Emphasis mine.)
Solution 3:
Consider threadbare
(Of cloth, clothing, or soft furnishings) becoming thin and tattered with age
(Of a person, building, or room) poor or shabby in appearance
[ODO]
I would also suggest worn-out[ODO sense 2] which is applicable for toiletries (toothbrush, shaving brush, razor etc..), clothing or furniture but may not be for gradually rearranged class room chairs.