I'm looking for a word that could replace the expression, broken-in as in "broken-in baseball gloves or a new pair of leather boots," meaning they are ready for comfortable use. Is there a simpler, shorter word that would convey the same message?
Worn-in, according to Wiktionary:
(of clothing) More comfortable as a result of having been worn often or for an extended period.
From the phrasal verb to wear in, according to Collins Dictionary:
if you wear in something such as a pair of shoes, you wear them until they fit your feet better and are more comfortable
In reply to Mitch's comment, I have searched for real-world examples of this use as an adjective, I have found some on the Outdoors SE:
But with well worn-in boots I always tend to get more blisters if I wear only one pair. source
Make sure you have proper hiking boots, which fit you well, and which are well worn in. source
2 "Wear in (phrasal Verb) Definition and Synonyms | Macmillan Dictionary." Grassroots (adjective) American English Definition and Synonyms | Macmillan Dictionary. Accessed May 10, 2018. https://www.macmillandictionary.com/dictionary/british/wear-in.
I’d suggest well-worn.
The OED defines it as:
Much worn or used; showing the signs of extensive use or wear.
The OP’s question mentions ready for comfortable use and breaking in. I think these are two different requirements. This answer is for the first one.
These leathers boots have been softened.
There are many articles online using this terminology for leather, e.g.
How to Soften Leather Shoes.
New leather shoes can be very painful, causing blisters and other foot-related problems. Unless you soften them, they will stay that way. Fortunately, there are several was to soften the leather, making it more comfortable for your feet. ...
Note: softening is not restricted to breaking in boots or baseball gloves by wearing them. It can instead refer to using oils or rubbing alcohol.
There are several meanings of "broken in", some of which are related to each other:
"The thief had broken in through the window" refers to the crime of "breaking and entering"; when for the purpose of intending to commit a further crime, this is covered by a separate offence of burglary under English law. The thief would be called a burglar, and we could say that he burgled the house.
"The porter broke into the conversation to point out that their train had arrived." Here the meaning is interrupted. The term break in, with this meaning, is commonly used among radio operators, eg. on board aircraft.
"The horse had to be broken in before it could be ridden." Here we could instead say tamed or trained, though that's not what a professional rider would say; they're still appropriate words for a layman character to use.
"I wore my new boots for a week, to ensure they were broken in, before I climbed the mountain." For this, worn in is two letters and a syllable shorter; I could also recommend conditioned as a single word. It's also possible to use softened in this context. A similar procedure applied to a new car would be run in.
A commonly used word to imply
broken-in (baseball gloves) meaning they are ready for comfortable use is preconditioned.
2 Brought into the desired state for use.
The following are results from Google search for "preconditioned gloves":
From https://goderichminorbaseball.ca/Pages/1056/Coach_s_Corner/: Preconditioned gloves mould around a hand much quicker and are quite comfortable for a young player.
From https://epdf.tips/the-little-league-guide-to-tee-ball-helping-beginning-players-develop-coordinati.html: Some glove manufacturers will offer preconditioned gloves, gloves that have been treated and mechanically broken in.