Answer the following Q with stream of consciousness. Context: An ovarian cyst is a fluid-filled sac within the ovary. Often they cause no symptoms. Occasionally they may produce bloating, lower abdominal pain, or lower back pain. The majority of cysts are harmless. If the cyst either breaks open or causes twisting of the ovary, it may cause severe pain. This may result in vomiting or feeling faint.

Question: what is meant by cyst in the ovary?
To answer this question, we should know that: An ovarian cyst is a fluid-filled sac within the ovary. Therefore, the final answer is a fluid - filled sac within the ovary.