n.

1. 活动；活动力[U]
   He once engaged in anti-government activity.

   他一度从事反政府的活动。

2. 行动[U]
   The store was a scene of great activity.

   这家商店顾客盈门。

3. 活跃；敏捷[U]
4. （某一团体的）特殊活动；带消遣性的活动[P1]
   The school offers many recreational activities for the students.

   该校为学生提供了很多娱乐活动。

   Many ended up in prison for terrorist activities.

   许多从事恐怖活动的人最终被关进牢房。

n.

1. a condition in which things are happening or being done.
   ▸busy or vigorous action or movement.
2. an action taken in pursuit of an objective.
   ▸a recreational pursuit.
3. the degree to which something displays its characteristic property or behaviour.