I've looked everywhere to find the meaning of this word and I can't find it. What's the definition of tesseract?

tesseract is the four-dimensional equivalent of a cube. This question took a little research, however, as ol' Cliff doesn't have all of the answers. The first place to look for the definition of a particular word, of course, is the dictionary. If you don't have a print dictionary handy, get on the Internet to check out some of the numerous online dictionaries. Start at the most obvious, Dictionary.com, and type in "tesseract." Click the "Search" button, and the definition appears. Another nice resource is Wikipedia, which is more like an encyclopedia than a dictionary, but it's amazingly helpful.