See also: Sipp English Noun SIPP (countable and uncountable, plural SIPPs) (travel, car hire) Acronym of standard interline passenger procedure, a series of four-letter codes used to indicate a type of vehicle. (UK, pensions) Acronym of self-invested personal pension. Anagrams IPPs, pips, PIPS, PPIs, PIPsWikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads