backslap

[bak-slap]
verb (used without object), back·slapped, back·slap·ping.
  1. to engage in backslapping.
noun
  1. a hearty slap on the back given as a token of affability or congratulation: The bridegroom received many a warm handshake and backslap.

Origin of backslap

First recorded in 1925–30; back1 + slap1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018