smack (someone) on the back

Translations
похлопать (кого-то) по спине
He smacked his friend on the back in congratulations.
Он похлопал друга по спине в знак поздравления.
Definitions
To hit or pat someone gently on the back, often as a gesture of encouragement, congratulations, or camaraderie.
Words
back

noun
обратная сторона
smack

verb
шлёпать