Plain English Meaning
An approach that uses GPS with WAAS to give you a precise side-to-side path to the runway, but does not tell you when to descend. You fly the centerline accurately, then level off at a set minimum altitude until you can see the runway.
Full Definition
A non-precision instrument approach procedure that uses WAAS (Wide Area Augmentation System) to provide lateral course guidance with localizer-like accuracy, but does not provide vertical guidance. The pilot flies the lateral track to a published Minimum Descent Altitude (MDA) and may only descend below that altitude when the required are in sight. LP are published at airports where or prevent the publication of an () approach.