The "straight rainbow" is a fairly unusual rank. To have a straight rainbow, you must hold 5 cards that qualify both as a straight and as a rainbow. In other words you must hold 5 cards with consecutive values and each suit is represented at least once. (Please see the sections on "Straights" and "Rainbows" for more precise definitions.) Below is an example of a "Straight Rainbow":
The cards represent each suit at least once and they have consecutive odd values (3, 4, 5, 6, 7).