Unlooked-for means something that came without anyone expecting it or asking for it. Almost always it is used for good things arriving by surprise: unlooked-for kindness, an unlooked-for gift, an unlooked-for chance to travel. That is what separates it from plain 'unexpected', which is neutral and can be bad news too. There is a warm feeling inside 'unlooked-for' — you were not searching for this, you had not earned it, and it came anyway. The picture inside the word is literal: you were not looking for it. It is old-fashioned and literary; you find it in novels and in careful writing, and you would rarely hear it in a Taipei office. The hyphen is normal and expected. It nearly always sits before a noun — you say 'an unlooked-for pleasure' rather than 'the pleasure was unlooked-for', though writers do occasionally do the latter for effect.

意想不到的、不期而遇的（多半指好事，帶「意外之喜」的味道）