ワンマン

わんまん
noun / na-adjective
one-man, autocratic, solo-operated
1. autocratic, dictatorial
Describes a person, especially a boss or leader, who makes all decisions alone without consulting others.
ワンマン社長(しゃちょう)だ。
He's an autocratic company president.
ワンマン経営(けいえい)では社員(しゃいん)がついてこない。
With autocratic management, employees won't follow along.
(かれ)のワンマンな態度(たいど)にみんな不満(ふまん)()っている。
Everyone is dissatisfied with his dictatorial attitude.
2. one-man, solo-operated
Operated by a single person, especially buses or trains that run without a conductor.
ワンマンバスに()る。
I ride a one-man bus.
この路線(ろせん)はワンマン運転(うんてん)だ。
This line operates with one-man (driverless conductor) service.
地方(ちほう)のバスはワンマン運行(うんこう)(おお)い。
Local buses mostly run as one-man operations.

ワンマン is wasei-eigo from English "one-man." It has two distinct uses in Japanese.

SENSE 1 — AUTOCRATIC:

Describes a leader who monopolizes decision-making. Almost always negative.

  • ワンマン社長(しゃちょう): autocratic president
  • ワンマン経営(けいえい): one-man management

SENSE 2 — SOLO-OPERATED:

Refers to public transport operated by a driver alone, without a separate conductor.

  • ワンマンバス: conductor-less bus
  • ワンマン運転(うんてん): one-man operation

NOTE:
In English, "one-man" is neutral, but in Japanese, sense 1 carries a strongly negative nuance. Sense 2 is a neutral, technical term used in transportation.