I have had a couple of people ask what this activity is. Impact Play isn't a common term used here in Australia, though I believe it is often used in the U.S. Simply put it literally means using force to create a contact, whether it be person to person or implement to human contact (spanking, whips, floggers, straps, canes etc) Nothing special really, just another term for discipline or corporal punishment.
Comments
Impact play
I have also heard it called "percussion play".
Some BDSM terms vary from country to country, even mistress to mistress.
For example, "forced feminisation" usually refers to cross dressing but some practitioners use this term for pegging (strap-on play). Obtaining clarification from the advertiser can be awkward.
I think advertising laws may help invent new terms for popular activities.
http://www.pla.qld.gov.au/advertising/
"Spanish", "French" and "Greek" are common euphemisms in Australia. Have you heard that in Germany BDSM activities are called "English" ?