Here is my suggestion: Cheese Tactics are tactics that rely on luck to be effective, and if you're unlucky they would put you behind.
[ Examples ]
If you go by this definition, 4/5/6pool is definitely cheese. You're basically hoping P FEs and doesn't scout you until it's too late to send probes to defend his warping cannons. If he went 2gate you're royally fucked, 5-6 probes + zealot can handle your lings well enough and your macro is horribly behind, not to mention he'll have 3 zea quickly.
Early pool in ZvT is retarded, you're basically hoping T doesn't wall, and if he does you already lost.
The only map where you'd want to 4/5/6 pool ZvT is Colosseum, for obvious reason. But even then, take note that 5pool lings come 20 seconds earlier than 9pool.
5pool in ZvZ loses to every single thing Z can do - 9pool, overpool, 12pool, even 12hat, are all a direct counter to 5pool, so if you earlypool in ZvZ shame on you, you won't be getting wins against any player ranked higher than D+ like that (or hell anyone that knows how to micro and how to ZvZ).
BBS is cheese because you're relying on countering a certain opening build, so that he can't respond. If his build was one that gives him the units to counter yours and he's not a complete noob, time to type gg.
5/6probe Proxy gates is cheese because, once again, you're basically relying on your opponent to have bad building placement to deal with the units from those gates and scouting them too late. If his simcity is good and/or he scouted them early, you just wasted a high amount of earlygame minerals and you have to play from a handicapped position.
Proxy robo is not cheese, it's clever play, when you do it you already scouted your opponent and you know his movement patterns so you know where to place it correctly. It's not any more cheese than Z's entire macro - where drone production relies entirely on anticipating the opponent's next move based on information you already have.
Hidden factory/rax float in TvZ isn't cheese because while it relies on not being scouted to truly be effective, it doesn't put you behind if it's scouted, it just won't give you an advantage.
So what do you people think about this definition?
- Relies on luck to be effective
- Puts you significantly behind if you were unlucky