It can also mean that it is a wave that causes the medium to vibrate at right angles to the direction in which the wave travels. Also, if you eat it, it turns into a giraffe, which turns into a lion, which turns into a black hole, which is actually purple. And shoots rainbows and lasers, which explodes into mushrooms, back hair and monkeys. Then the monkey eat your face, and throw it back up onto you. You are now immortal.