From The Collaborative International Dictionary of English v.0.48 :
Piu \Pi"[`u]\, adv. [It., fr. L. plus. See Plus.] (Mus.)
A little more; as, pi[`u] allegro, a little more briskly.
[1913 Webster]
From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
PIU
Path Information Unit (IBM, SNA)
From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
PIU
Plug-In Unit