What defines being on tilt is such an interesting subject. Reading through all these answers I can agree that these answers are totally great answers that are relevant to recognizing when one is on tilt. I can also say from my playing experience that I have found exception with most of those answers, I have played angry, I have targeted players, and a number of those other specifics on the list and it was wise to do so in the particular situation. I like the answer from Nick Larsen in this respect most.
Not being able to get a handle on your tilt is the most negative thing to winning that most poker players experience. Tilt is the opposite of being in the zone. You know the zone when you see it, cards come and you understand perfectly how to play them. Tilt being the opposite is when cards do not come and you do not understand how to play them.
One of the basic rules I have for myself is when the cards do not come and I do not understand how to play them, I get out of the game. This rule for me came about because I felt that if I was losing in strange and unexplainable ways that I could not explain simply, something was going on with the game I did not understand like cheating, or something was going on with me I could not understand. Either way time to go home.
When you keep getting very unlucky your on tilt rather you realize or not. If nothing is working your are not in the zig of being in the zone, you are in the zag of being in tilt land. Tilt may or may not be any of those symptoms described. (Not discounting those symptoms, if your loosing and you have one or more of them it is a stronger indicator you are on tilt). If you are not in something that is closer to the zone then to tilt, you are more tilted then not, and if you are loosing, rather or not your feeling like your playing bad, you need to get up and do what ever works best for you to get your head back on straight.
Tilt is not necessarily an emotion. Tilt to me is some mindset that keeps one from being correct enough to beat a particular game. Tilt to me is not an absolute thing it is a variable thing. One can be cool calm and collected, feeling rested and good about their game, then sit down in a game they simply do not have a grasp of, and their ego keeps them playing. This is a form of tilt. If you sit down and do not understand why you are loosing and stay, you have made an irrational tilted move.
Many reasons you might be loosing that you do not quite understand. Your being cheated by a team. They look like crappy players, but you just can't get the handle on them. You have tells that other players are picking up with a good degree of accuracy. We all have tells, and most of the time we are not that readable, but sometimes without realizing it we are. It is an irrational act of ego, that keeps us playing. It is irrational because we do not understand why we are loosing, why we are so far out of the zone and leaned toward tilt, and yet we keep playing.
Playing on tilt is degenerate gambling. One of the signs of degenerate behavior, rather it is drinking, drugs, sex or gambling is rationalization. This is were you attempt to convince yourself and others that what your doing is the right thing to be doing. If you are rationalizing to yourself, to your playing friends, you are indeed to far out of the zone and into tilt land. If your trying to convince everyone that this guy is playing badly and you can beat him, you are rationalizing. If you are convinced your playing well and yet they fold on your big hands and you have not successfully bluffed all night, you are rationalizing. if you keep trying to convince yourself that it will change because of this or that, you are rationalizing. Rationalizing is simply one of the surest signs that you or more tilted then in the zone.
The question How do you recognize when you are playing “on tilt”? Is the most important part of the game of poker a player can master. Tilt is insidious, some players overcome it for awhile, do not really have a problem with it for years or even decades, then it hits them so badly the bankroll goes, and they end up in GA or just walk away. As we have all heard most big name players have gone broke, some many times. They can't walk away for awhile when things go bad. Tilt busted me more then once.