To slap with one's penis
"That bitch wouldnt suck me..so I gave her a nice big meat slap."
The act of slapping a piece of red meat as hard as physically possible. A test of how good a piece of meat is, usually performed in ASDA. The louder the noise, the better meat quality. If the slap is pitiful, then the meat is off/not of decent quality, and should not be bought.
Don't buy that gammon, it sounded shit when I gave it a meat slap