Search Result for "tripling": 
Wordnet 3.0

NOUN (1)

1. increase by a factor of three;

The Collaborative International Dictionary of English v.0.48:

Triple \Tri"ple\, v. i. [imp. & p. p. Tripled; p. pr. & vb. n. Tripling.] [Cf. F. tripler. See Triple, a.] To make threefold, or thrice as much or as many; to treble; as, to triple the tax on coffee. [1913 Webster]
WordNet (r) 3.0 (2006):

tripling n 1: increase by a factor of three