n.
Function: adjective
Date: 1548
1 a : running away : FUGITIVE b : leaving to gain special advantages (as lower wages) or avoid disadvantages (as governmental or union restrictions) < runaway shipping firms> <a runaway shop>
2 : accomplished by elopement or during flight
3 : won by or having a long lead <a runaway success> also : extremely successful <a runaway best seller>
4 : subject to uncontrolled changes < runaway inflation>
5 : being or operating out of control <a runaway oil well> <a runaway nuclear reactor>