#1 compression n. [compaction, concretion, densification] an increase in the density of something. wn
#2 compression n. [condensation, contraction] the process or result of becoming smaller or pressed together; "the contraction of a gas on cooling". wn
#3 compression n. encoding information while reducing the bandwidth or bits required. wn
#4 compression n. [compressing] applying pressure. wn
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