The term used if a person shits out of something, goes home early on a night out, or basically stops doing something that in all situations should be done with ease.
E.g.
A person goes home from a night out really early
"You propa half-seshed it last night didnt you, went home early"

And

"Are you coming on the new oblivion ride at alton towers?" "No" "You Half-sesh"
by rego_jacko November 19, 2008
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a person who can't handle his drink
"Oi, Keano, you're a pua Half Sesh"
by pualad March 1, 2013
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