The definition of irrationality is extremely vague. Yet, considering how often it is used as an objection to an argument, a precise definition is important.
Is domestic violence 'irrational?' It's called irrational because it nets you no material advantage, and we all know it's unhealthy, but is it actually irrational?
The problem is that I have to assume that the abuser nets some psychological payoff from the abuse, because otherwise they would stop - violence is expensive and risks harm from the victim's defensive reactions, which translate directly into psychological costs.
As a result, while the apparent reasons for the abuse - generally punishment - are clearly meretricious, there are in fact actual reasons. The abuser's situation is better if they abuse, at least insofar as the abuser is capable of perceiving alternatives.
That doesn't sound irrational to me. Quite the opposite.
Similarly terrorism, especially suicide terrorism. It is not irrational, it is merely an act in search of unknown payoffs, most likely psychological and/or purely subjective payoffs. (The political payoffs can't be rational directly because of course the terrorist ends up dead. The politics can lead to psychological payoffs, however.)
In the scientific conception, belief in God is irrational because the standard of proof is discontinuous. Evidence and logic is used for all temporal matters, but this method is not used with relation to God, despite the fact that, for instance, ID attempts to use logic and evidence against the atheist.
Again, we see that irrational can be held to mean simply deceptive, usually self-deception. It is well known that God holds psychological payoffs for believers. How exactly is it 'rational' for believers to give up a demonstrably effective belief simply because it happens to be false? It is also usually false that atheism will give any benefit to the former believer, a falsity often refuted by atheists. (As I would expect, regardless.)
In short, the definition of irrationality is abused early and often.
I'm hereby restricting valid uses of irrationality to two.
First, acts or beliefs that lead to only negative outcomes.
Second, acts of logic that violate the laws of logic. When an argument leads the receiver to conclude something in contradiction to the argument. Or, when fallacious arguments are considered, even after someone points out the fallacy, to be useful, true, or convincing.
Let us consider the irrational fears.
Obviously, fearing harmless things do not lead to any beneficial outcomes. (However, once you have a fear, respecting it is the best idea - trying to ignore your phobia will likely lead to psychological harm.) In this sense, phobias are irrational.
Similary, most phobias are acquired through irrational event chains, where a false conclusion is drawn, but then reinforces itself.
AI's science you can do at home series has something for you here. You can try this with not stepping on sidewalk cracks. I also did it once with the ghosts circling the ghost houses in Mario World. Induct a phobia in yourself by avoiding, through all means possible, stepping on a crack, or being on a ghost house square when the ghost is in front. If you firmly establish the habit, especially if you come up with a superstitious reason for the habit,* it becomes emotionally difficult to stop. The phobia is born and starts being self-reinforcing.
My use of irrationality will not include non-rationality. For instance, since there are no predictive differences, the choice between free will and determinism is a non-rational choice. Similarly which perspective you take on objective vs. subjective reality.
This type of irrationality is, I believe, the reason for all philosophical disputes that are not axiom wars. Because logic is perceived by the mind,* irrationality is insuperable in a debate. There is no argument you can make that can repair someone's mind from the outside.
*Sally is in Baltimore. Baltimore is in England. Therefore, Sally is in England. Now, for the acid test. How do you know Sally is in Baltimore? As in, not the source of the knowledge, but the actual method, the actual how?
That process, the process through which you know Sally is in Baltimore, is the same process that lets you chain England into Sally. If that process is interrupted, it does not look interrupted on the inside - instead it leads to irrationality, to false conclusions.