Their faces were alit with happiness.是什么意思？

Their faces were alit with happiness.

他们脸上喜气洋洋

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

faces

n. 面容( face的名词复数 )，表面，脸，方面；v. 面对( face的第三人称单数 )，面向…，正视，承认；

例句
Smiles, nods, and cheerful faces added to the general gaiety.
微笑、点头和喜洋洋的脸庞使喜庆的气氛变得更浓了。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

alit

n. 铝铁岩；vi. alight的过去式和过去分词；v. 飞落( alight的过去式和过去分词 )，突然注意到，偶然发现（或想到）；

例句
La r é alit é , quelle est - elle?
什么是事实?

with

prep. 和，跟，随着，关于，和…一致；

例句
A waiter entered with a tray...
侍者端着托盘进来了。

happiness

n. 幸福，高兴，恰当，合适；

例句
It is my dearest hope that one day she will find the happiness she truly deserves.
我最大的期望就是她有一天能够找到真正应得的幸福。