His cause of death being foul play is improbable.
Are you asking for a sentence using the word? Try, It is improbable you are smart enough to graduate from high school.
That's an improbable story.
I might win the lottery, but it is improbable.
A response to this question is improbable. Your recommendation of my answer is also, equally improbable. It is improbable that you will find my answer helpful. There. Three examples.
It was improbable that they would find the cache.
My admission to med school is quite improbable.
Your improbable story makes good copy- I'll print it!
Implausible is an adjective which means improbable, unlikely, unbelievable, or incredible. Example sentence: The plot of that movie was implausible, I'm not recommending it.
Improbable is the word.
That I would vote for him, given his platform, is highly improbable, since I disagree with him. It is improbable that a baby is born knowing how to walk or talk.
It is improbable that the sun were to crash into the earth.It is improbable that you would get struck by lighting at this very moment.The girl found a conclusion to a problem by canceling out the improbable answers.
The word "improperble" does not exist in standard English vocabulary or dictionaries. It seems to be a made-up or non-standard word. Therefore, it cannot be used in a sentence according to standard English grammar.