I would like to suggest that we try to come up with several defintions of rationality. I don't feel we have exhausted this search area by any means. Robin has suggested, "More "rational" means better believing what is true, given one's limited info and analysis resources". Other commenters have emphasised goal-directed behaviour as a necessary ingredience of rationality. I think these defintions miss out on several important ingrediences - such as the social nature of rationality. There is also a subtext which argues - that rationality only gives one (correct) answer even if we only can approximate it. I feel strongly that rationality can give several correct answers and thus imagination is an ingredience of rationality. So without in any way believing that I have found the one correct defintion, I propose the following: When two or more brains try to be sensible about things and expand their agency. I believe that "sensible" in this context does not need to be defined as it is a primitive and each player willl submit their own meaning.
Maybe this is a can of worms - but are there other suggestions or defintions for rationality we can apply in our lives?
Arguing over definitions is pointless, and somewhat dangerous. If we define the word "rational" in some sort of site-specific way, we risk confusing outsiders who come here and who haven't read the prior threads.
Use the word "rational" or "rationality" whenever the difference between its possible senses does not matter. When the difference matters, just use more specific terminology.
General rule: When terms are confusing, it is better to use different terms than to have fights over meanings. Indeed, your impulse to fight for the word-you-want should be deeply suspect; wanting to affiliate our ideas with pleasant-sounding words is very similar to our desire to affiliate with high-status others; it makes us (or our ideas) appealing for reasons that are unrelated to the correctness or usefulness of what we are saying.
Arguing over definitions is pointless if we're trying to name ideas. Arguing over definitions is absolutely necessary if there's disagreement over how to understand the stated positions of a third party. Establishing clear definitions is extremely important.
If someone has committed themselves to rationality, it's natural for us to ask "what do they mean by 'rationality'?" They should already have a clear and ready definition, which once provided, we can use to understand their commitment.