Noun
1. any specific activity;
"they avoided all recreational activity"2. the state of being active;
"his sphere of activity""he is out of action"3. an organic process that takes place in the body;
"respiratory activity"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"6. the trait of being active; moving or acting rapidly and energetically;
"the level of activity declines with age"