Expander can refer to: · Part of the process of audio level compression · Part of the process of signal compression · Part of the process of companding · MIDI processor, hardware or software, to synthesize sounds from MIDI commands · Turboexpander, a turbine for high-pressure gas · Expander graph, a sparse graph used in the combinatorics branch of mathematics · StuffIt Expander, a file decompressor software utility · "Expander", a song on the album Accelerator by The Future Sound of London · Orthodontic expander, a device to widen the upper jaw