The Collaborative International Dictionary of English v.0.48:
L-P \L-P\, LP \LP\n. [long-playing.] a long-playing phonograph record; designed to be played at 33.3 rpm. [Acronym] [WordNet 1.5]WordNet (r) 3.0 (2006):
L-P n 1: a long-playing phonograph record; designed to be played at 33.3 rpm [syn: LP, L-P]