This is a very absurd question, I know. Because there is no particular answer to this, not any specific rules to refine the meaning of our life. It's so different for all of us.
But I usually make an answer to satisfy me for this type of question. This is also very simple to understand. And that is, make ourselves valuable to others through our work.
We all adds value, make an impact on others life in different ways. It can be through what we do as a living or can be just our way of life. Now, when we start to notice this and adds value positively, that's when we will learn how meaningful our lives are.
Maybe your job helps others passively. But when you start some volunteering activities, you can feel how you are impacting on society or as a whole. This perception can change our life for the better.
Think what you can do to make this world a better place. Think this keeping aside your personal benefit. Most of the time we spend a huge portion of our life running to fulfill our own personal desire. And this makes us miss the part -adding values. I'm not saying we have to leave our dreams and start to think about helping others. But we certainly can choose to add values to others' lives through our work, no matter what we do. Our determination and realization are what matters most here.
I know this sounds simple but when we evaluate and start to relate this to our life, finding meaning would seem hard. But I can tell you shifting our focus from 'thyself' to 'others' can be the best option.