1.
place one has gone out to; destination when out; while out
Where someone is when they're out of the house or office — the workplace they've visited, a café, a station, etc. Often appears with で to mean "while out and about."
Compound of 外出 (going out) + 先 (destination, place of). The 先 suffix is the same one in 勤務先 (workplace) and 連絡先 (contact info).
Common collocations
Usage
Very common in announcements and modern work-from-anywhere contexts: 外出先でも対応可能 ("can respond even when out"). Less common in casual conversation, where people usually name the specific place instead.