cu·bic / ˈkyoōbik/ • adj. having the shape of a cube: a cubic room. ∎ denoting a unit of measurement equal to the volume of a cube whose side is one of the linear unit specified: 15 billion cubic meters of water. ∎ measured or expressed in such units. ∎ involving the cube (and no higher power) of a quantity or variable: a cubic equation. ∎ of or denoting a crystal system or three-dimensional geometric arrangement having three equal axes at right angles.• n. Math. a cubic equation, or a curve described by one.DERIVATIVES: cu·bi·cal adj.cu·bi·cal·ly / -ik(ə)lē/ adv.