A person who cannot control their gag reflex, even during times of laughter.
After drinking too much water, the person cannot do anything but project the recently swallowed water with some mucous. This makes the person a Gwinny.
Used to describe a person you find annoying/pathetic/hopeless or just plain distasteful. Originates from a name used to describe the zombies in Nazi Zombies when you grenade their legs off.
"Bob is such a Gwinny! When he lost his ray gun, i nearly punched him."
"Dylan felt like such a Gwinny when he swapped his ray gun for a sniper."
"Savvas punched Bob for being a Gwinny about his ray gun."