1. A computer-implemented method of searching for information in an information retrieval system, the computer-implemented method comprising: receiving a search query comprising a plurality of terms; selecting one of the plurality of terms, wherein unselected terms of the plurality of terms comprise remaining terms of the received search query and the selected term has a position relative to the remaining unselected terms of the received search query; selecting, for the selected term, a replacement term that appears in a plurality of previously received multi-term search queries in a same position within the previously received multi-term search queries as the position of the selected term relative to the remaining unselected terms of the received search query; deriving an altered query by replacing the selected term in the received query with a disjunction of the selected term and the replacement term; and generating a list of search results for the altered query.