To parry just means to “ward off”, “deflect”, or “redirect”. You don’t need a sword to do it, it can be done with your hands or even with wordplay. However, it’s not actually interchangeable with block which is how it gets used a lot in fiction.
Now, that’s actually what will decide whether your writer is accurately using the term or not. Not the word itself, but what’s happening in the fight itself.
If it involves turning the blade aside or knocking it away then that’s a parry.
If they’re referring to stopping the enemy blade so that they clash together then that’s a block.
Generally parries involve connecting with the edge of the blade, though they can connect with the flat. The main goal of the parry is to deflect the enemy blade away from yourself, this creates an opening to riposte or launch counter attack now that their enemy’s defenses are weakened. This why in professional fights and most sparring matches you see a lot more testing with smaller strikes, gauging their opponent’s defenses, their reflexes, and their timing before they fully commit to a strike.
Block, parry, then riposte.
Here’s Billy Grandy discussing and talking about drills to teach parrying with a longsword. This will help you get a better grasp of shape and motion when editing for your writer, and maybe it’ll get less repetitious.
Here’s Matt Easton talking about flat blade parries.
With swords, especially long swords, a good way to think about it is
“riding the edge”. That’s not technical, that’s just how I think about
it when I’m writing swordplay. The blades connect and the sword slides up or down the edge as it’s flicked outward by the rotation or tilted on an angle.
A challenge for your writer:
If I see the same word come up a lot in my writing so much so that it’s become a crutch, I often challenge myself to try using a different one. If it’s a technical term, I challenge myself to describe the action itself.
It’s very easy to trap yourself in a repetitive state where you don’t really know what you’re describing and hoping that the technical terms will carry you through. However, there’s a difference between the general gist of a term and it’s actuality. The understanding which comes from being able to describe the act of parrying and show it’s importance in swordplay in the fight scene itself is what will make their fight sequences better. It will make their writing better.
The same is true for the rest of our followers, if you see yourself using the same sentence structure a lot then try to change it up. Try new things. Phrase it a different way. Look up your favorite words. Try to discover what other words could be used to describe an action. If you find yourself falling back on technical terms rather than technical details in the hopes that they will carry you through, take some time to look up what the technical terms themselves involve.
For example, if you find yourself using “parry” a lot try this:
He caught the incoming strike along his blade’s edge and, rotating the pommel with his off hand, turned it aside.
That is a parry with a sword like a claymore which requires two hands to wield. We never used the technical term, but now the reader has a better idea of what it is.