Answer: A drug that alters brain functions and leads to change in emotions, consciousness and mood of a person.
Explanation: It is a combination of two words; Psycho and Active.
Psycho meaning relating to the wellness of the mind and body.
And Active meaning working or in action.
So, a psychoactive drug is a pharmaceutical product that changes the function of the brain which leads to alterations in behavior and cognition.
They are used for both medical and recreational purposes.
Some of these include; stimulants, antidepressants and anaesthetics.
Psychoactive drugs usually cause brain alterations which the user may find rewarding and which could subsequently lead to addiction.