what is the appropriate verb/phrase to describe

I cannot think of a single British English word for the state. There are some words and phrases to describe a person in such a state. We have a hyphenated phrase, "stay-at-home", which one could use to describe a person who rarely or never goes out.

The phrase carries no implication of introversion though. As always, context is important. For example, a "stay-at-home father" is a man who, contrary to widespread practice, is the partner in a marriage who stays at home and cares for the children while the mother goes out to work during the day.

A person might say "Since I bought my HD television and my new sofa, I have become a stay-at-home".

I wonder if you are thinking of a person who just does not go out as often as other people, or a person who literally never goes out, who is probably mentally ill or disabled? (In the latter situation, we say they are "housebound".)

So, you would have to use a phrase such as "introverted stay-at-home".

Perhaps the word "hermit" would fit the purpose?

The term "shut-in" might work. One definition refers to someone who is sick and can't go out. Here's another definition I found:

Disposed to avoid social contact; excessively withdrawn or introverted.

That's a good one, Roberta. It can also mean a person who cannot get out even if they want to. When I was a Christian teenager (I have been an atheist for 40 years) a group of us used to go to peoples houses and hold mini-services for them. It was called "ministering to shut-ins".

thanks contrex and roberta for your detailed explanations.

since i needed a verb, i googled a bit following your suggestion of 'hermit', and found that people are saying 'i'm hermitting' quite often now.

seems this is a new usage of this word and is gaining popularity in some informal context (which is my case). i found an entry on merriam-webster, where 'hermit' is used as a transitive verb (unlike in most other informal contexts).

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Hermitting (verb) : To lock oneself away from the rest of the World.
I have been hermitting myself away from everyone anymore. ?-Kim H., Manifesto of Life, 2007

http://www3.merriam-webster.com/opendictionary/newword_display_alpha.php?letter=H&last=170
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interesting

Try "cocooning" and "agoraphobic"

glad you saw the light, contrx.

thanks username (that's a funny username:)).
i like 'cocooning'!

(don't let contrex hear you say that--it's an Americanism, and he'll get all steamy).

cocooning, how vivid. i'm in LA, so i guess i can use it .

i do find one advantage of british english though -- there's a distinct pronunciation difference between 'can't' and 'can'. here in america, i often could not tell and have to say 'pardon me' several times.

"HOMEBODY" is another expression.