Something that cannot take place or exist because physical limitations prevent it from happening. For example, two pieces of matter cannot occupy the same space because it is physically impossible.

In philosophy, physical impossibility is the second strongest type of impossibility. Logical impossible is stronger. Psychological impossible is weaker.

Physical impossibility implies that a non-contradictory system could be worked out in which it is possible. (It's not possible in this universe, but there could be a universe in which it would be possible).