(idiomatic) In a single attempt with no breaks.

plural of one-dayer

Placed in a situation where one's best behaviour is necessary or advisable.

(golf) A handicap of one stroke every second hole.

As far as concerns one.

(UK, military, slang) A first lieutenant in the navy.

With the consent of all; unanimously.

Synonym of for one's life

A carnival freak show that presents numerous exhibits in the same location.

(automotive) The first finished, saleable car of a new model to come off the production line.