The Collaborative International Dictionary of English v.0.48:
fast-growing \fast-growing\ adj. tending to spread quickly; -- used mostly of plants. [prenominal] [Narrower terms: invasive (vs. noninvasive) ] Syn: aggressive. [WordNet 1.5]WordNet (r) 3.0 (2006):
fast-growing adj 1: tending to spread quickly; "an aggressive tumor" [syn: {aggressive, fast-growing(a), strong-growing]