push-down list: a list in which the next item to be removed is the item most recently stored (LIFO)
message: what a communication that is about something is about
alpha receptor: receptors postulated to exist on nerve cell membranes of the sympathetic nervous system in order to explain the specificity of certain agents that affect only some sympathetic activities (such as vasoconstriction and relaxation of intestinal muscles and contraction of smooth muscles)