Final answer:
The state of adaptation with a withdrawal syndrome caused by stopping or reducing a drug is known as Dependence. It involves physical and/or psychological withdrawal symptoms when the drug is not consumed.
Step-by-step explanation:
The state of adaptation characterized by a drug class-specific withdrawal syndrome that can be triggered by abrupt cessation, rapid dose reduction, or administration of an antagonist is known as Dependence. This condition manifests when the body has adjusted to the presence of a drug, and cessation of the drug leads to physical and/or psychological withdrawal symptoms. It's essential to discern between other states such as tolerance, which occurs when a drug user requires more and more of a given drug to experience the same effects, and psychological dependence, which refers to the craving for a drug.