re·ac·tive 
/riˈæktɪv/ adjective
/riˈæktɪv/ adjective 1 [more reactive; most reactive] : done in response to a problem or situation : reacting to problems when they occur instead of doing something to prevent them
▪ a reactive strategy ▪ The government's response to the problem was reactive rather than proactive. — compare proactive 2 chemistry : tending to change into something else when mixed with another substance
▪ a reactive chemical/substance
▪ a reactive strategy ▪ The government's response to the problem was reactive rather than proactive. — compare proactive
▪ a reactive chemical/substance
