A blow delivered with the open hand or with something flat.
Hold your jaw, or I'll slap your mouth for you, you lying thief! – Tempest and Sunshine by Mary J. Holmes
Ha, ha, ha, do not provoke me, lest I take you a slap in the Face, I tell you that now. – The Works of Aphra Behn, Vol. I (of 6) by Aphra Behn