To touch someone or something gently and usually repeatedly with the hand flat. (Cambridge Dictionary)
Touch quickly and gently with the flat of the hand. (Oxford Dictionaries)
A light blow especially with the hand or a flat instrument. (Merriam – Webster)
If you pat something or someone, you tap them lightly, usually with your hand held flat. (Collins Dictionary)
Example
Clip art. Basic words.
https://www.abcteach.com/documents/clip-art-basic-words-pat-color-labeled-i-abcteachcom-37602