No in a sense the word uncommon would mean more rare in most contexts, nonstandard, you could say, unconventional, unorthodox, irregular, etc.
The boy was a nonstandard student.
we were using the nonstandard set of measurements
You could add the prefix non- to it to make the word nonstandard.
There is no widely-recognized definition for "fludger." It may be a made-up or uncommon term with no specific meaning.
true
yes
There is no commonly accepted definition for the term "insoulable." It is possible that it may be a misspelling or a rare or uncommon word.
C. Tuckey has written: 'Nonstandard methods in the calculus of variations' -- subject(s): Calculus of variations, Nonstandard mathematical analysis
You can invent any number of nonstandard units, but none of them is "best". It is best to use standard units, that is, the meter.
This statement is false. Many speakers of nonstandard English may be literate in their own language variety, and literacy rates vary across different populations. It is important to recognize and respect linguistic diversity, including nonstandard varieties of English.
There is no widely recognized meaning for the name "Jasitha." It could be a unique or uncommon name with no specific definition.
"Uphelion" appears to be a made-up or uncommon word. It does not have a widely recognized definition or usage in the English language.