| Noun | 1. | butterfly effect - the phenomenon whereby a small change at one place in a complex system can have large effects elsewhere, e.g., a butterfly flapping its wings in Rio de Janeiro might change the weather in Chicagoconsequence, effect, result, upshot, outcome, event, issue - a phenomenon that follows and is caused by some previous phenomenon; "the magnetic effect was greater when the rod was lengthwise"; "his decision had depressing consequences for business"; "he acted very wise after the event" | |