Your "opposite" sign is the one that is directly, well, opposite your own on the "wheel" that comprises the 12 signs of the zodiac. "Opposites" are sometimes said to be either perfectly wonderful, or perfectly horrible together.
My husband is also my Opposite (my Pisces to his Virgo.) I'll have been married to him for thirty years come February, so it's obviously not all bad! :)
BTW, most traditional astrologers would consider Leo and Aquarius to be a very good match.
I'm a Leo and oppisite to an Aquaruis
I'm Sagittarius having a relationship with a Gemini for 8 years, guess what? We're engaged! Opposites do attract.
Omg ima Aquarius and my new boyfriend is a Leo he makes me feel like I' m on top of the world he is something new to the table and im happy to have him