infusion /infyo̅o̅″zhən/ [L, in, within, fundere, to pour] , 1. the introduction of a substance, such as a fluid, electrolyte, nutrient, or drug, directly into a vein or interstitially by means of gravity flow. Sterile techniques are maintained, the equipment is periodically checked for mechanical difficulties, and the patient is observed for swelling at the site of injection and for cardiac or respiratory difficulties. Compare injection, instillation, insufflate. 2. the substance introduced into the body by infusion. 3. the steeping of a substance, such as an herb, to extract its medicinal properties. 4. a liquid preparation made by pouring water over plant parts (such as dried or fresh leaves, flowers, fruits) and allowing the mixture to steep. Boiling water is usually used, but cold water may also be used. Making a cup of herbal tea is an example. −infuse, v.
