Whack \Whack\, v. i.
To strike anything with a smart blow.
[1913 Webster]
{To whack away}, to continue striking heavy blows;
as, to whack away at a log. [Colloq.]
[1913 Webster]
"Smooch" is a very mildly irreverent way to refer to a kiss
A "high-five" is when you smack your palm against someone else's palm
(the person is expecting it).It is a specific action