What is the medical term meaning administration of a medication by injection?

The correct answer is parenteral.

非経口という用語は、消化管以外の経路による薬物またはその他の物質の投与を記述するために使用される医療用語です。 This includes injections, infusions, and topical applications. Parenteral administration is often used when rapid absorption or a precise dose is required, or when the medication cannot be taken orally.