To strike someone or something with a sharp slap or blow, especially with the open hand. She smacked the mosquito on her arm before it could bite her.
To make a sharp sound with the lips, often as a sign of enjoyment or satisfaction. He smacked his lips after tasting the delicious dessert.
To hit something with a loud noise. The ball smacked against the wall with a loud thud.
To carry the flavor, quality, or suggestion of something; to seem to be strongly characteristic of. The whole scheme smacks of corruption.
To kiss someone loudly or noisily. She smacked him on the lips as soon as he walked through the door.