Austin asks:
"What would you consider to be a biblical definition of the term ‘drugs’? What do you believe to be a reasonable biblical definition of the term ‘intoxication’?"
Your first question I will address in this post while the second part I have addressed previously in another post. Please see that article for a discussion of what constitutes Biblical intoxication.
What are drugs?
Since you also mentioned intoxication, I assume that when you ask for a "biblical definition of the term drugs" you mean that class of substances that produce what many would consider negative health effects (such as cocaine, heroin, or LSD for example). Therefore, I will only be dealing with that usage of the word "drugs" in that context.
The Bible does not contain specific verses on any term that resembles the word "drugs"--only passages about how the Christian should treat his or her body. Consequently, those passages are the only ones the Christian can look to when considering the topic of drugs. The most prominent of these is 1 Corinthians 6:19-20, which states:
"19 Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; 20 you were bought at a price. Therefore honor God with your bodies."
This passage makes it abundantly clear that using such drugs that produce negative health effects would be a violation of God's intent for the human body and consequently be sinful. If using anything that harms your body is sinful, and "drugs" would fall into that category, one comes to your original question: what are "drugs?"
Since the Bible has no word or concept similar to what most people mean by "drugs," I have turned to several dictionary definitions (relating to the negative usage of the word):
U.S. Federal Food, Drug, and Cosmetic Act, subchapter 2, section 321 G (1938)
"articles (other than food) intended to affect the structure or any function of the body of man or other animals;"
Merriam-Webster Online Dictionary, © 2013
"3: something and often an illegal substance that causes addiction, habituation, or a marked change in consciousness"
Oxford Dictionaries, © 2013
"a substance taken for its narcotic or stimulant effects, often illegally"
The first definition is the current legal definition of "drug" as defined by the main law concerning drugs that the FDA enforces. This definition is not much help, because "helpful drugs" (e.g. aspirin) would be (and are) applicable to this definition.
Both Merriam-Webster and Oxford Dictionaries define "drugs" (that cause negative health effects) using two criteria: (1) the substance significantly alters one's state of mind and (2) the substance is obtained or used illegally. I think this two-pronged approach to the meaning of the word "drug" is Biblical. This would be so because the Bible would, as seen above, be against someone using drugs (even with that word ambiguously defined)--therefore it would have to be the case that "drugs" are, by definition, sinful in their nature. Since the Christian is obliged to obey God-ordained authority (see Romans 13), it would follow that any illegal substance--especially one that is illegal because it produces negative health effects--would be wrong for the Christian to use.
Concerning the first part of the two-pronged approach--that drugs change one's state of mind--I think it is also acceptable to consider this a Biblical definition. Jesus once healed a demon-possessed man whose healing included the Disciples finding the man "dressed and in his right mind" (Mark 5:15). Thus, it is apparent that Jesus wishes for mankind to be in his or her right mind and therefore any substance that would change one's state of mind in a negative way would be sinful to use.
When these two ideas are brought together, it creates a reasonably broad, Biblical definition of "drugs" for the Christian to employ. A "drug," for the Christian, is any substance that changes one's state of mind in a negative way (and intoxication via alcohol consumption would certainly fall under that definition as well) and is also illegal according to the authority under which the Christian finds him or herself.
It occurs to me that one might argue "but has not God created everything? Why would He make substances that have the potential to hurt man so greatly?" The appropriate answer is that sin is the lack of what is good--it is not an existential reality of itself. I remember Dr. Charles Stanley once preached that sin is "anything God-given that is used beyond its God-given boundaries." The Coca plant (from which cocaine is made), for example, is actually used medicinally to treat altitude sickness--processing it to make cocaine is therefore a perversion of what was once good. Thus, God created things such as the coca plant, the opium poppy (from which morphine and through that heroin is made), and ergot fungi (from which LSD is ultimately created) for different, good purposes in His Creation that man subsequently purposely misused for evil objectives.
I hope my thoughts were helpful, Austin! Thank you for the question.
God bless,
Robert A. Rowlett