Intentionally losing the game or hurting your teams chances of winning (even if that team is just you) is gamethrowing.
My question is about how a jester votes, because situations like this come up a lot. A sample scenario is there is only a Confirmed SK, a Confirmed Vet, and a jester still alive. The SK openly tries to convince the vet to lynch the Jester (so he himself does not get lynched) and the SK casts a vote to put the jester on trial, but the Vet votes the SK. My question is, is it gamethrowing if the Jester votes to lynch the SK here. He is guaranteed to lose if he does this (which seems like a direct violation of the gamethrowing rule as it's worded), while if he doesn't there is a chance the vet will reconsider and lynch him.