An example of estranged used as an adjective is in the phrase an "estranged sibling" which means a sibling that someone hasn't spoken to in a long time.
- simple past tense and past participle of estrange
- She estranged her husband by not talking to him for over a year.
(comparative more estranged, superlative most estranged)
- Having become a stranger, of one who formerly was close, as a relative, friend, lover, or spouse.
A relatively formal term, the more colloquial alternative is “to not talk”, as in “I don’t talk to my mother”. A semi-formal alternative is not on speaking terms.