- not permeable; impassable.
- Chemistry, Geology. (of porous substances, rocks, etc.) not permitting the passage of a fluid through the pores, interstices, etc.
- (of a substance) not allowing the passage of a fluid through interstices; not permeable
- Impossible to permeate; not permitting passage.
- Relating to a material through which substances, such as liquids or gases, cannot pass. Some substances, such as some types of contact lenses, are permeable to gas but impermeable to liquid.