To hit something with a loud sound, like when you hit your lips together when you eat something tasty.
Smacks can be a fun sound when eating something good, but it can also be a sound of hitting something hard.
Examples:
She smacks her lips after eating the yummy cookie.
The ball smacks the wall and bounces back.
He smacks the table with his hand to get everyone's attention.
The wind smacks my face when I run fast.
The thunder smacks the sky and makes a big noise.
The door smacks shut when the wind blows.
To have a taste or smell of something.
Smacks can be a good taste or smell, like when you taste something delicious, or it can be a bad taste or smell, like when something tastes or smells bad.
Examples:
The soup smacks of garlic and onions.
The air smacks of rain.
The cake smacks sweet and yummy.
The fish smacks bad and I don't want to eat it.
The flower smacks good and makes me happy.
The room smacks of old socks and I don't like it.