What's a bulwark?

"A mighty fortress is our God, a bulwark never failing. . . "

You know how you've sung certain songs or hymns for years?
Then one day you look at the text and you say, "What on this blessed green earth is a bulwark?"
I kind of knew, given the context, what a bulwark is.
But, honestly, if someone asked me to define bulwark and use it in a sentence, could I?
How about "constrained"
or "girded"?
And what's the difference between "cherubim" and "seraphim"?

There's a comfort to singing or speaking these words. They fit within the context of church or religion, or worship. We understand, by faith and tradition that "bulwark" or "girded" are acceptable words to use, even if we can't quite explain their meaning.

"Bulwark" is defined in the dictionary as a defensive wall, especially of earth, a rampart.

But what if you looked up "bulwark" and suddenly discovered that the comforting word you've been singing in the old hymn, "A Might Fortress is our God" is now defined as. . .
bulwark: a thin, transparent film of plastic used to provide a buffer from the wind.

?

Now how mighty is God when He merely shelters you from wind, but not from fire, arrows, bullets or an army?

Words are evolving. Words like "freedom" or "tolerance" or "respect." There are many others.
Their new definitions may or may not yet be included in your dictionary.
But ask your children to define words commonly used in their social studies classes and you may get a surprise.

Thank God "bulwark" is still a defensive wall, able to hold back the enemy.
And God is still mighty in "A Mighty Fortress."