3 definitions by Chaint.

The region between the balls and the arse-hole; can be an erogenous zone for some.

Girl: I was fingering that part between his balls and his arse and there was shit there.
Everyone listening remained silent but later laughed among themselves:
'Eww! He had a shitty chad.'

When you measure your dick, you don't start at the arse-hole and include the chad; you risk getting shit on your measuring tape.

The region between the balls and the arse-hole; can be an erogenous zone for some.

Girl: I was fingering that part between his balls and his arse and there was shit there.
Everyone listening remained silent but later laughed among themselves:

'Eww! He had a shitty chad.'

Short for 'shit yes!'

Which became 'shit yeah!'

When said fast it then became 'shitchyeah' and evolved to just:

'chyeah!