meantime

名词 meantime:

1. the time between one event, process, or period and another
   同义词：interim, meanwhile, lag

副词 meantime:

1. during the intervening time
   同义词：meanwhile, in the meantime

1. I like skiing and in the meantime, I know it is very dangerous.
   我喜欢滑雪，同时也知道这非常危险。
2. Physicists are studying new ways of generating electricity with less damage to the environment. In the meantime, many power plants are being modernized to give off less polluting material.
   物理学家们正在研究对环境危害少的发电新方法，与此同时，许多发电厂也在实现现代化以减少污染物质的释放量。
3. You buy the fruits, in the meantime I'll cook breakfast.
   你去买水果，同时我来做早餐。

mean.time

n.（名词）
The time between one occurrence and another; an interval.
当中时间：一个与另一个出现间的时间；间隔
adv.（副词）
During a period of intervening time; meanwhile.
在间隔时间内；与此同时

Meantime is more common than meanwhile as a noun:
meantime 作为名词比 meanwhile 更为普遍：
例句：
In the meantime we waited.
我们在这时等待着。

As an adverbmeantime is less common than meanwhile :
作为副词meantime 不及 meanwhile 普遍：
例句：
Meanwhile we waited.
与此同时，我们等候着。

All of these uses are standard, however.
但是这些用法都是标准的