Offline means not connected to the internet. Work offline, an offline copy, go offline.
It has come to mean unavailable as much as disconnected — a server that is offline is down. Offline also means away from the internet altogether: offline friends, offline life. In a meeting, taking something offline means discussing it afterwards, which is a business idiom that has drifted a long way from the technical sense.
1adjectiveofflineNot connected to the internet.
“My phone was offline during the flight, so I missed all your messages.”
2adjectivealtogetherAway from the internet altogether.
“On holiday, I like to go offline completely and leave my phone at the hotel.”
offline is a state of disconnection.
Off plus line, from the sense of a communication line. Online was formed the same way and is older in industrial use.
From off- + line.
Etymology from Wiktionary, CC BY-SA
Practised in Technology & Internet