means The forceful effect, influence, or collision of one thing striking against another — whether a literal crash or a lasting change.

from From Latin 'impactus,' the past participle of 'impingere' — to drive into, to push against — built from 'in-' (into) plus 'pangere' (to fix, fasten, or strike). For its first centuries in English it meant a physical wedging or striking together; the figurative sense of 'a strong effect on someone or something' is comparatively modern, and the verb 'to impact' (as in 'this impacts us') is more recent still — which is why it can sound jarring to some ears.