The act of waking up on a Sunday morning, smoking some weed, and then chilling and enjoying yourself.
Any very relaxed, laid back seshes that take place in the daytime. May come on the tail end of a really crazy night.
A: How was your weekend? I heard about the party on Saturday...
B: Yeah it was lame as fuck, it got broken up after like a hour. I did crack a Sunday Sesh the day after though, which was pretty chill.
Short for "sunday session". The act of getting together on a Sunday to socialise and drink likely large amounts of alchohol.
"I know we've been out Friday and Saturday, but fancy coming down to the pub for a Sunday sesh?!".
"On my way."