mountain railway; funicular
Refers to a railway that ascends a mountain, often a funicular or a scenic mountain train.
The Hakone mountain railway is especially popular during the autumn foliage season.
ケーブルカー specifically refers to a cable car or funicular, while 登山電車 is a broader term for any mountain railway, including rack railways.
Compound of 登山 (tozan, 'mountain climbing') and 電車 (densha, 'electric train'). The term straightforwardly describes an electric train used for ascending mountains.