epinephrine /ˌɛp.ɪˈnɛ.fɹɪn/ noun1 •A catecholamine hormone and neurotransmitter; as a hormone, secreted by the adrenal gland in response to stress (when it stimulates the autonomic nervous system); as a neurotransmitter, synthesized from norepinephrine. It is also used as a medication.At the ER, after deflating me with a cocktail of epinephrine, a steroid and an antihistamine, the doctors scolded me for not coming in more quickly: I could have died of asphyxiation. — 2023 formsepinephrines