Definition of pat:
(n) :
the sound of a light slap or tap with a soft flat object, especially of a footstep; a light tap or slap, especially with the hands
(v) :
to (gently)
tap the flat of one's
hand on a
person or thing; to hit lightly and repeatedly with the flat of the hand to make smooth or flat
"to show affection, he decided he would pat the boy on the head."