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?
Sure, it is useful to ask for clarification when we don't understand what someone is saying. But we don't need to settle on one "correct" meaning of the term in order to accomplish this. We can just recognize that the word is used to refer to a combination of characteristics that cognitive activity might possess. I.e. "rationality" usually refers to thinking that is correct, clear, justified by available evidence, free of logical errors, non-circular, and goal-promoting. Sometimes this general sense may not be specific enough, particularly where different aspects of rationality conflict with each other. But then we should use other words, not seek to make rationality into a different concept.
"But we don't need to settle on one "correct" meaning of the term in order to accomplish this. "
We do in order to understand what we're saying, and for others to understand us. Switching back and forth between different meanings can not only confuse other people but confuse ourselves.
To reach truly justified conclusions, our reasoning must be logically equivalent to syllogisms, with all of the precision and none of the ambiguity that implies.