What does it mean there is a probable cyst in the right love of the thyroid gland measuring 9 by 6 mm?

Very common: Thyroid nodules are very common. About 70% of the population has a nodule (many don't know it). About 5% of nodules are cancerous, which is why we care. Unless there were concerning characteristics on the ultrasound like microcalcifications, taller than wide or increased blood flow or you have a family history or radiation exposure, typically we just follow-up with an annual ultrasound.

Thyroid cyst: It means that the radiologist reading the ultrasound sees a nodule that is cystic not solid, containing fluid. The fact that it is probable means that it is not definite, likely because it is relatively small in size.