sem|i|per|me|a|ble «SEHM ee PUR mee uh buhl», adjective.
partly permeable; permeable to some substances but not to others. A semipermeable membrane allows the solvent, but usually not the dissolved substance, to pass through. »
If salt water and fresh water are separated in a chamber by a semipermeable membrane, the fresh water will flow through the membrane into the salt water (Luna B. Leopold).
Useful english dictionary. 2012.