Source : Webster's Revised Unabridged Dictionary (1913)

Activity \Ac*tiv"i*ty\, n.; pl. {Activities}. [Cf. F.
   activit['e], LL. activitas.]
   The state or quality of being active; nimbleness; agility;
   vigorous action or operation; energy; active force; as, an
   increasing variety of human activities. ``The activity of
   toil.'' --Palfrey.

   Syn: Liveliness; briskness; quickness.

Source : WordNet®

activity
     n 1: any specific activity; "they avoided all recreational
          activity" [ant: {inactivity}]
     2: the state of being active; "his sphere of activity"; "he is
        out of action" [syn: {action}, {activeness}] [ant: {inaction},
         {inaction}, {inaction}]
     3: an organic process that takes place in the body;
        "respiratory activity" [syn: {bodily process}, {body
        process}, {bodily function}]
     4: (chemistry) the capacity of a substance to take part in a
        chemical reaction; "catalytic activity"
     5: a process existing in or produced by nature (rather than by
        the intent of human beings); "the action of natural
        forces"; "volcanic activity" [syn: {natural process}, {natural
        action}, {action}]
     6: the trait of being active; moving or acting rapidly and
        energetically; "the level of activity declines with age"
        [syn: {activeness}] [ant: {inactiveness}]