Tending to spread quickly; -- used mostly of plants. (adjective)
Gnu Collaboartive International Dictionary of English: licensed under The Code Project Open License (CPOL)
Use "fast-growing" in a sentence
"It's also matching wits with the smartphone/tablet world, namely the fast-growing crowd of GOOG Android devices."
"He would now witness thousands of fire-new terms flowing generously into the lexicon that he had augmented and renewed, and would probably recognize some kinships between the fast-growing English vocabulary of his world and of ours.xvii"
"Meanwhile, Peru's fast-growing economy presents a big opportunity for many Brazilian companies well-placed to take advantage of massive infrastructure and energy projects now planned or underway."