Adjective has 2 senses

• proactive(a = adj.all) - descriptive of any event or stimulus or process that has an effect on events or stimuli or processes that occur subsequently; "proactive inhibition"; "proactive interference"

Antonym: retroactive

• proactive(s = adj.all) - (of a policy or person or action) controlling a situation by causing something to happen rather than waiting to respond to it after it happens;