To ponder: to weigh in the mind; to consider especially quietly, soberly,and deeply.
"But Mary kept these all these things, pondering them in her heart".Lk 2:19
How right Merriam Webster is: pondering is not merely thinking about a thing. To ponder is to keep something in your heart, to consider it quietly, soberly, and deeply, as St. Luke tells us Mary did at the birth of her son.
She weighed in her mind the knowledge that her savior had been born. While every one else was amazed and talked about it with great excitement, Mary kept it in her heart. She was quiet, she was sober... solemn... grave... with the import of what had occurred, and she took it all deep within herself.
The dignity of Mary is striking. She preserved her modesty by keeping what was hers to herself. We might think she was reserved... maybe even a little cold in her quiet reflection. I certainly thought of Mary as distant, impossibly perfect, and untouched by the events happening around her: Angels delivering messages? The Messiah born at last... as her son? Fleeing to Egypt based on a dream? No big deal. She won't let any of it distract her from being serene and composed.
The truth, of course, is something else indeed. The magnitude... the importance... of the event deserves some quiet thought; it is worthy of pondering.