das Antibiotikum, Antibiotika

Meaning (in English):
An Antibiotikum is an antibiotic: a medication used to kill bacteria or inhibit their growth in order to treat bacterial infections. (It does not work against viruses such as those causing most colds or flu.)

Multiple meanings / usage

• Medical sense (most common): a drug used to treat bacterial infections (e.g., penicillin).
• Broader/scientific sense: a substance (often originally produced by microorganisms) that inhibits or destroys bacteria; in modern usage this also includes many synthetically produced antibacterial agents.

Word parts (etymology / components)

• anti- = “against”
• bio- = “life”
• -tikum / -ikum = a common ending in names of medicines/substances
  So the term literally suggests something “against (certain) living organisms,” specifically bacteria in medical usage.

German synonyms

• Antibiotika (plural; often used generically)
• antibakterielles Mittel (antibacterial agent)
• Bakterienhemmer (bacteria inhibitor; less common)
• Bakterienkiller (colloquial)

German antonyms (if applicable)

There is no single fixed opposite, but depending on context:

• Virostatikum (antiviral medication; “against viruses” rather than bacteria)
• Probiotikum (probiotic; supports beneficial bacteria rather than killing them)
• Nährmedium (growth medium; something that promotes microbial growth, in laboratory context)