Wiktionary
n. (context music informal English) An electronic musical instrument that generates sounds by replaying samples stored in ROM, unable to synthesize sounds or to record new samples.
Wikipedia
A rompler is an electronic music instrument that plays audio samples stored in ROM chips to generate sound. In contrast to samplers, romplers do not record audio and have limited or no capability for generating original waveforms. The term rompler is a portmanteau of the terms ROM and sampler. Both may have additional sound editing features, such as layering several waveforms and modulation with ADSR envelopes and LFOs.
Romplers are often packaged as music hardware sound modules, such as the E-mu Proteus line of products and the Roland U-20. Almost all digital pianos and many electronic keyboards (such as Yamaha PSR-290) are romplers. The term rompler may also describe software instruments such as VSTis). These do not have the ability to record new samples; instead, samples are replayed from computer RAM after they are loaded from disk. Popular examples of software romplers are reFX Nexus and IK Multimedia Sampletank. In this context, a software instrument can only be considered a rompler if it restricts the user to certain bundled sounds, without allowing them to load their own samples.