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not writing or contacting for a while; neglecting (failing) to write (call, visit, etc.); long silence
ご無沙汰しております、お元気ですか。
It's been a while — how have you been?
長い間ご無沙汰して申し訳ありません。
I apologize for not being in touch for so long.
ご無沙汰の友人から突然手紙が届いた。
A letter suddenly arrived from a friend I hadn't heard from in a while.