boarding door; entrance (vehicle)
Refers to the door or entrance used for boarding a vehicle such as a bus, train, or taxi. Often contrasted with 降り口 (alighting exit).
See also: 降り口
Is the bus boarding door at the front or the back?
My ticket was checked at the train entrance.
horse mounting equipment
Only with reading のりくち
Archaic term for equipment used to restrain and mount horses. Reading restricted to のりくち.
Old documents record 乗り口 as a type of horse equipment.
Standard kanji spelling for the common reading のりぐち.
Irregular okurigana variant; less common and may be considered non-standard.
Compound of 乗り (boarding) + 口 (opening, entrance). The archaic horse-equipment sense is a specialized historical usage.