A railway line that branches from the trunk line and then rejoins it at another point.(noun)
Gnu Collaboartive International Dictionary of English: licensed under The Code Project Open License (CPOL)
Use "loop-line" in a sentence
"From Bourg a loop-line traverses a picturesque country by Nantua to Geneva, 97 m."
"E. by loop-line from the station St. Auban on the main line."
"S.W. from Arvant, commences the loop-line of the Chemins de Fer du Midi, which traverses the lofty woodless highlands of Lozère, the coal-region of Aveyron, and the wine and olive department of Herault to Beziers on the Mediterranean line, between Cette and Narbonne."