backslapping

/B AE1 K S L AE0 P IH0 NG/
verb
  1. 1

    To enthusiastically affirm or congratulate a person, especially by patting them on the back.

noun
  1. 1

    Action of the verb to backslap

Source: https://en.wiktionary.org/wiki/backslap, https://en.wiktionary.org/wiki/backslapping