Noah Webster's Dictionary (n.) A rushing onward; an onset; a verbal or physical assault.

Multi-Version Concordance Onrush (2 Occurrences) Job 41:29 A thick stick is no better than a leaf of grass, and he makes sport of the onrush of the spear. (BBE) Ezekiel 30:16 And I will put a fire in Egypt; Syene will be twisting in pain, and No will be broken into, as by the onrush of waters. (BBE)