Slang for sex from behind while standing. The receiving party will usually need to lean on tour something stable i.e. a wall, sink or heavy furniture keeping them on the ball of their feet or tips of their toes.
It’s not just a hit song by Tiny Tim, it’s when you insert your toe between the two lips of a woman’s vagina. One can insert the whole toe, or just the tip. May also refer to the lips of the mouth.
When Tiny Tim slips the tip of his toe through Big June’s pussy lips, he is tiptoeing through the tulips.