The symbol | tells the corpus interface to look for either of the two words you’ve entered, so clean|dirty dishes (no space) would return dirty dishes and clean dishes. It can be inserted anywhere in your search string and can be used for multiple (not just two) words. Thus, if you’re interested in which things are cleared, put, tidied, or stowed away, you can find out by using this search string: clear|put|tidy|stow away _nn*

It’s even possible to look for two (or more) different parts of speech by using the old syntax. “pretty [j*]|[r*]”, for example, finds “pretty” followed by an adjective or an adverb.

You can find complete overviews of the search syntax in the BYU interface, the Lancaster BNC interface, AntConc and regular expressions in AntConc here.