1. [adj]  having five units or components
2. [v]  increase fivefold; "The population of China quintupled"

QUINTUPLE is a 9 letter word that starts with Q.

1. \Quin"tu*ple\, a. [L. quintus fifth: cf. F. quintuple,
   L. quintuplex. Cf. {Quadruple}.]
   Multiplied by five; increased to five times the amount;
   fivefold.
   
   {Quintuple time} (Mus.), a time having five beats in a
      measure. It is seldom used.
   
   

2. \Quin"tu*ple\, v. t. [imp. & p. p. {Quintupled}; p.
   pr. & vb. n. {Quintupling}.] [Cf. F. quintupler.]
   To make fivefold, or five times as much or many.