I'm fairly sure I've addressed the subject of Meaningful Action several times over, but—having come to a new(er) understanding of it—I'm going to address it again.
Meaningful action is what everything that happens in a story should be. Or, more specifically, what everything the writer relates in the narrative should be. Although a character might bath, groom themselves, and spend half an hour picking out duds, none of this is meaningful action unless it's somehow directly tied into the plot (like that character is being watched while doing so, or the water is full of nanites, or the clothes are magical, or...).
A minor exception can be made for actions that must be depicted so the reader isn't confused, as well as action that reveals character (although ideally these should be Meaningful as well, serving several purposes at once). Everything else is filler and should be gotten rid off, or, better yet, not included in the first place.
Just as importantly, Meaningful Action is directly tied to a character's motivation, usually the main character(s) and usually related to a try-fail cycle. Everything that happens in a story should be directed by a character for the purpose of accomplishing a goal and/or thwarting the goal of another.
Yes, overcoming environmental hazards or being presented with them counts (a volcano erupts, the temperature suddenly drops below freezing, etc). But be aware that survival, in and of itself, is rarely interesting enough to drive a story. Survival placed at odds with an important goal (making a run on the Death Star) is much more compelling.
So... undirected, aimless action (whether 'exciting' or not) is not healthy for a story. A reader should always feel as though the viewpoint character is acting in a way that that character believes will bring them closer to a goal. The goal should always be transparent (no false mystery!) and the action should always be explicable, if not logical (in other words: 'in character').
Action must have resolution. A character must succeed or fail, and it must be clear to the reader whether that character has succeeded or failed. Ideally, failure (excepting ultimate failure as in a tragedy) should leave room for a new approach to surmounting whatever obstacle the character has failed to surmount—whether over, around, or through.
Failure must not be relieved by coincidence (Deus Ex Machina). Coincidence is difficult to swallow in any instance, but some level of it is present in all fiction. Coincidence that saves the day robs a story of relevance. Action must have unavoidable consequences in order to feel real.Characters must have agency.
A story is a situation, acted on by a character in a meaningful way, leading to results that are clearly causally connected to the action taken by that character. No more and no less.
I'm as guilty as anybody of muffing all this stuff (like writing an awesome gunfight that is actually a snooze-fest, because it isn't actually relevant). Guiltier than most, probably. But laying it out like this, in a very clear and succinct (almost harsh) form, is immensely useful for me as a cribsheet I can refer to later, or a mental map (like a transparency) I can lay on top of my stories, then say "Hmm... is this actually a compelling Story?"