VSI may stand for: Vertical shaft impactor, a type of impact crusher Vertical speed indicator, an instrument in an aircraft monitoring rate of descent or climb Very Short Introductions, a series of books published by Oxford University Press Virtual Switching Instance, in VPLS Voluntary Service International, the Irish branch of Service Civil International VMS Software Inc. A vendor/supporter of OpenVMS related software. VSI Group, British dubbing and translation company VSI Berlin GmbH, German subsidiary VSI Translation & Subtitling BV, Dutch subsidiary Vendor's Single Interest insurance, a type of insurance that only protects the lien holder, as opposed to dual coverage insurance Voltage Source Inverter, DC to AC converter