DeMundo 144:1 :ܪܘܚܐ ܒܥܢܢܐ ܥܒܝܛܬܐ ܘܬܠܝܠܬܐ܃ ܟܕ ܢܙܕܪܒ ܩܛܝܪܐܝܬ ܠܡܣܕܩ ܥܒܝܘܬܗ ܕܥܢܢܐ‏ : a wind in a thick and moist cloud, when it is forcefully compressed to split the cloud's thickness
See the entire entry for zrb vb. to press, to compress