What does under par mean?
The phrase under par means “disappointing because it is below the expected standard” (e.g., “Although somewhat under par for a movie from this director, it’s still definitely worth seeing).
“Feeling under par” means feeling slightly unwell (e.g., “I was feeling a bit under par this morning, but I’m full of energy now”).
“Under par” is a golfing analogy. In golf, “par” is the number of shots it should take an excellent golfer to complete a particular hole, so it has a meaning similar to “average.”
Have you tried QuillBot’s Grammar Checker? You can use it to help check that you’re using the phrase “under par” correctly in your writing.