旁观的英文：
spectator
non-participant

参考例句：

Stand by; look on
站在一旁;旁观

To watch from the sideline without interfering
缩手旁观

Look on; gaze on
观望;旁观;看;以为

An attitude of calm indifference
冷静旁观的态度

An impartial onlooker must be sought out.
须问旁观冷眼人.

Onlookers left the pavement and fell in alongside the marching demonstrators.
旁观的人离开人行道，加入游行示威的队伍。

'It is true,'said Defarge, who was kneeling to look on and hear.
“这倒是真的，”德伐日说，此时他正跪在地上旁观，听着他们说话。

Here, of course, we, who are outside the tank, enjoy a hearty laugh
我们这些站在魔箱以外旁观的人，看到此处不免哈哈大笑。

spectator是什么意思：
n. 观众，目击者，旁观者

A crush of spectators.
极度拥挤的观众

The game drew thousands of spectators.
这场比赛吸引了数千名观众。

The game drew thousands of spectators.
这场比赛吸引了数千名观众。

non是什么意思：
pref. 非；不

The alkanes are non-polar.
烷是非极性的。

non-bumper seesaw
防撞跷跷板

non-Euclidean norm
非欧几里得范数

participant是什么意思：
n. 参与者；参加者

She is an active participant in this activity.
她积极参与这项活动。

Their assent to participate must be documented.
必须用文件来证明他们同意参加研究。

unfitness that bars you from participation.
因为不胜任而不能得到参与某项工作的资格。