Platonic describes a relationship that is purely spiritual and not physical. If a guy and a girl hang out all the time but aren't boyfriend and girlfriend, they'd describe their friendship as platonic.
This word platonic refers to the writings of Plato, an ancient Greek philosopher who wrote on the interesting subject of love. Platonic love and platonic friendships are marked by the absence of physical or sexual desire. Plato did acknowledge physical desire, but thought that if two people truly inspired each other, their spiritual or ideal love would bring them closer to God.