noun

The action of effusively congratulating or encouraging someone, typically by slapping a person’s back.

effusive displays of backslapping and arm-punching

adjective

Vigorously hearty.

those cheerful, backslapping journalists

friendly,genial,affable,amiable,congenial,agreeable,good-humoured,cordial,warm,sociable,outgoing,gregarious,clubbable,companionable,hail-fellow-well-met