Porous/ˈpɔːrəs/ Definition 1 of 2Pro Tip 1/3Literal Holes Porous describes actual small openings in materials where air or liquid can pass through. Porous rocks can hold water. Pro Tip 2/3Absorption Quality Materials described as porous often absorb substances, which is why they're used in filters and sponges. Porous fabrics are great for cleaning spills. Pro Tip 3/3Physical Texture A porous object may feel rough due to the many tiny holes it has on its surface. You can see the porous texture on the pumice stone.