默哀的英文：
1.observe a moment of silence in tribute
2.mourn
3.stand in silent tribute

参考例句：

Would it be seemly to have a moment of silence for the Iraqi corpses?
如果我们为伊拉克阵亡战士默哀片刻，会不会不大礼貌？

They took off their hats by the grave in silent salute.
他们在墓旁脱帽默哀.

They took off their hats by the grave and held a moment of silence.
他们在墓旁脱帽默哀。

Let us stand in silent tribute to the martyrs!
大家起立，为死难的烈士们默哀！

We will not forget moments of silence and days of mourning in Australia and Africa and Latin America.
我们不会忘记那些在澳大利亚、在非洲和拉丁美洲为我们默哀和悲痛的人们。

Let us hold a moment of silence in order that we remember those who died to preserve our freedom.
让我们默哀片刻，以缅怀那些为维护我们的自由而牺牲了的人们。

observe是什么意思：
v. 观察；注意到；遵守；评论

We observed the barometer fall. [The barometer was observed to fall.]
我们看见晴雨表下降。

Observation is the best teacher.
观察是最好的老师。

They observed the behavior of their new pet.
他们观察他们新宠物的生活习性。

moment是什么意思：
n. 片刻，瞬间；时机；重要；力矩，矩

at this exigent moment
在此危急关头

On the spur of the moment
一时冲动

stalling moment
失速力矩|使气流离体力矩

silence是什么意思：
n. 寂静，沉默，拒绝回答，互相不通音信的情形
v. 使安静，压制
int. 安静！别作声！

The children were awed into silence.
孩子们吓得不敢作声。

end play silencer
轴端间隙减声器

Great souls suffer in silence
伟人受苦,声色不露