It doesn't defy gravity literally, but the anti-gravity monument does take a defiant stand toward what its originator once called "Our Enemy No. 1."
Gravity was Roger Babson's nemesis and obsession ever since his sister drowned when he was a teenager. Babson blamed gravity, and when he later became a millionaire businessman he founded the Gravity Research Foundation to find a way to defeat it. He also gave money and stock to over a dozen colleges and universities if they placed one of his inspirational tombstone-like monuments on their campuses. Tampa's went up in 1965, inscribed "to remind students of the blessings forthcoming when science determines what gravity is, how it works, and how it may be controlled."
Babson died in 1967 but his monuments remain. Gravity, which makes big rocks too heavy to move, turned out to be his friend after all.