The word parenteral comes from greek <<para->> “παρα-” which means beyond and <<-enteron>> -ἔντερον which means intestine. In the healthcare area the parenteral pathway indicate the entrance of a substance through a pathway which is not absorbed by the intestine (i.e. which is not taken as oral or anal pathwaies as food , a pill, a sirup, a suppository, a bacteria ext.). The term parenteral actually indicate each and every pathwaies that do not include intestinal absorption. In many cases it is implied that a parenteral pathway indicate an injection (intravenous injection, intramuscular injection, subcutaneous injection, intradermic injection ext.); although it is not the only way.
The intake of a substance parenteral via can be adventitious, leading to the formation of an infection (bacteria or viruses can enter the organism for example through cutis lesions or in any other case that do not involve the intestine).
The intake of a substance parenteral via can be intentional, and in this case we can talk about parenteral administration of a nutrient (Fleboclisys i.e. intravenous feeding) or of a drug.