adj relating to, or securing, proportion.
2. proportional ·noun any number or quantity in a proportion; as, a mean proportional.
3. proportional ·noun the combining weight or equivalent of an element.
4. proportional ·adj having a due proportion, or comparative relation; being in suitable proportion or degree; as, the parts of an edifice are proportional.
5. proportional ·adj constituting a proportion; having the same, or a constant, ratio; as, proportional quantities; momentum is proportional to quantity of matter.