It seems like you might be trying to say "pentagenarian," which is a word sometimes used to describe someone who is in their 50s. It's a less common term than "quinquagenarian" but follows a similar pattern.
Here's the breakdown:
* Penta- means five (like "pentagon" - a five-sided shape)
* Genarian refers to a decade of life (like "sexagenarian" for someone in their 60s)
So, while "pentagenarian" isn't in widespread use, it technically refers to someone between the ages of 50 and 59.