backslap

listen to the pronunciation of backslap
Английский Язык - Английский Язык
to display excessive or effusive goodwill or cordiality (to someone)
{i} affectionate and sincere slap on the back given as to express congratulation or admiration or compliments
{f} display or demonstrate exuberant goodwill; treat a person or one another in an affectionate cheerful complimentary manner
display excessive cordiality (towards); "he is always backslapping his colleagues at staff meetings