1.chemical agent capable of activity
2.the voice used to indicate that the grammatical subject of the verb is performing the action or causing the happening denoted by the verb;
`The boy threw the ball' uses the active voice
3.a person devoted to the active life
4.tending to become more severe or wider in scope;
active tuberculosis
5.engaged in or ready for military or naval operations;
on active duty
6.disposed to take action or effectuate change;
a director who takes an active interest in corporate operations
7.taking part in an activity;
an active member of the club
8.characterized by energetic activity;
an active toddler
9.exerting influence or producing an effect;
an active ingredient
10.full of activity or engaged in continuous activity;
an active seaport
11.in operation;
keep hope alive
12.of the sun; characterized by a high level activity in sunspots and flares and radio emissions
13. expressing that the subject of the sentence has the semantic function of actor: "Hemingway favors active constructions"
14. expressing action rather than a state of being; used of verbs (e.g. `to run') and participial adjectives (e.g. `running' in `running water')
15. (of e.g. volcanos) erupting or liable to erupt;
active volcanos
16. producing activity or change
17. engaged in full-time work;
active duty
18. being in physical motion;
active fish in the aquarium
19. characterized by energetic bodily activity;
tennis is an active sport