(Discrete Cosine Transform) An algorithm that is widely used for data compression. Similar to Fast Fourier Transform, DCT converts data (pixels, waveforms, etc.) into sets of frequencies. The first frequencies in the set are the most meaningful; the latter, the least. To compress data, the least meaningful frequencies are stripped away based on allowable resolution loss. DCT is used to compress JPEG, MPEG, DV and H.263 frames.