English Noun SLP (plural SLPs) Initialism of speech-language pathologist. Initialism of super long play. See also (super long play) EP LP SP Proper noun SLP Initialism of San Luis Potosí, a state of Mexico. (Philippines) Initialism of Sustainable Livelihood Program. Anagrams pls, PLs, LPS, PSl., LPs, P&Ls, PSL, P/Ls, LSP, SPL Swahili Noun SLP Initialism of sanduku la Posta (“post office box”).Wikiwand - on Seamless Wikipedia browsing. On steroids.