Phobia
noun, suffix
You learned 恐怖 means "terror," and 〜症 can mean "disease." So what's a terror disease? Well, it's a phobia.
In Japanese, 恐怖症 is mostly used as a suffix for specific phobia names, like 高所恐怖症 (acrophobia, or fear of heights). Do you have any 恐怖症?
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
私も父も高所恐怖症です。
My dad and I are both afraid of heights.