When you use several different methods to do something, it's multimodal. A multimodal presentation might involve giving a speech while referring to a poster that's illustrated with pictures of your main points.
Anything that makes use of more than one technique can be described as multimodal, like your favorite graphic novel, which includes both written text and illustrations. This term shows up a lot in statistics, too, for statistical distributions with several peaks, or "modes." Multimodal comes from the Latin roots multus, "many," and modus, "manner or mode."