Definition of "rectilineal" [rec•ti•lin•e•al]

• Alternative form of rectilinear. (adjective)

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• "It must, however, be remembered that rays have no physical existence, for it is the waves that are propagated, and not the ray, which simply indicates the direction that the light takes, this truth being known as the rectilineal propagation of light."
• "Under the centripetal force, the base of the projectile tended toward the moon; but the centrifugal still prevailed; and it was probable that its rectilineal course would be changed to a curve of some sort, the nature of which they could not at present determine."
• "The first law of motion is, that everything preserves a state of rest, or of uniform rectilineal (that is, straight, motion), unless affected by some moving force."