injection:The action of forcing a fluid, etc. into a passage or cavity, as by means of a syringe, or by some impulsive force; esp. the introduction in this way of a liquid or other substance into the vessels or cavities of the body, either for medicinal purposes, or (in a dead body or portion of one) in order to exhibit the structure or preserve the tissues. ——Oxford English Dictionary

injection: an act of putting a drug into someone’s body using a special needle. ——Longman Dictionary of Contemporary English  @en