What does SPIW stand for?

ESCAP - Economic and Social Commssion for the Asia and Pacific Division for Shipping, Ports, and Inland Waterways (EAIO)

Shipping, Ports and Inland Waterways (SAUS)

Special Purpose Individual Weapon (SAUS)

Special-Purpose Individual Weapon - A rifle that fires flechettes or darts - Pronounced "spew"

Special-Purpose Infantry Weapon (SAUS)