The story
Borrowed from Japanese ミニ新幹線(しんかんせん) (mini shinkansen). By surface analysis, mini- + shinkansen.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A conventional Japanese rail line which has been upgraded to allow use by shinkansen; generally to allow the continuation of shinkansen services beyond the end of a purpose-built, high-speed line. Full definition →
Borrowed from Japanese ミニ新幹線(しんかんせん) (mini shinkansen). By surface analysis, mini- + shinkansen.
Etymology from Wiktionary, CC BY-SA 4.0.