looker-on

In nothing is this more clear (to the looker-on at the game) than in the endless disputes concerning restrictions on commerce.
The Collected Works of Ambrose Bierce|Ambrose Bierce
But a flirtation, after all, unless in a one-act comedy, is not entertaining to the mere looker-on; and oh!
In the Days of My Youth|Amelia Ann Blandford Edwards
The most casual looker-on might have seen the change taking place in his patient day by day and he was not a casual looker-on.
Robin|Frances Hodgson Burnett
As a looker-on I've seen a lot of the game called marriage, and I'd know how to make you happy.
Married Life|May Edginton

You know our plan, and you must see that as only one can act in it, your part would be that of a mere looker-on.
An Egyptian Princess, Complete|Georg Ebers

Origin of looker-on