Refers to a less-traveled road or path that avoids the main route, often used to save time or avoid congestion.
I used a back road to avoid the traffic jam.
Only locals know this byway.
Compound of 抜け (nuke, 'escaping' or 'passing through') and 裏 (ura, 'back' or 'rear'), literally 'back passage'. The exact historical derivation is uncertain, but the word is conventionally associated with the meaning of a bypass or back road.