activity/ækˋtIvətI; ækˈtIvəti or ækˈtIvIti/n plural activities 1 [C usually plural 一般用复数] something that you do for enjoyment in a regular organized way〔为了娱乐而经常从事的〕活动: leisure/recreational/social etc activities outdoor activities such as hiking and climbing 远足和登山之类的户外活动2 [C,U] things that people do to achieve a particular aim〔为达到某种目的而从事的〕活动﹐行动: political/business/economic etc activity the department's research activities 系里的研究活动terrorist activity 恐怖活动3 [U] when a lot of things are happening, or when people are moving around [ inactivity ] 热闹﹐活跃: The house is full of activity once the kids get home. 孩子们一回来﹐家里就很热闹。