To knowingly or unknowingly shake someone's hand directly after having a shit without washing ur hands, the other person might be too embarrassed to sniff their hands after the shit handshake.
I'm gonna give him/her a shit handshake.
To deliberately shake hands with someone, upon using the shitter without washing your hands directly after wiping your arsehole. Example: "I bumped into Mr Villos today on my way back from the shitter & I gave that Malaka a shitty handshake, stupid bastard didn't even realise that I didn't wash my hands after wiping, as I was happily shaking his hand".
I bumped into Mr Villos today on my way back from the shitter & I gave that Malaka a shitty handshake.