Final answer:
A strong acid or base is defined as a substance that ionizes completely in solution, resulting in a high concentration of H+ or OH- ions and making them good conductors of electricity.
Step-by-step explanation:
A strong acid (or base) is one which ionizes completely in solution.
This means that a strong acid or base dissociates fully in water, producing a high concentration of hydrogen ions (H+) or hydroxide ions (OH-) respectively.
As a result, strong acids and bases are good conductors of electricity due to the presence of these ions in solution.
In contrast, a substance with a high molecular weight, a weak electrolyte, or a substance that does not dissolve in water does not define a strong acid or base.