1. A method for performing an image search using semantic entities, the method comprising: receiving, by one or more computing devices having one or more processors, a target image as a search query; identifying, by the one or more processors, at least one similar image that has at least one feature in common with the target image, the at least one similar image associated with one or more semantic entities, wherein each semantic entity defines a concept with a particular ontology; determining, by the one or more processors, at least one likely semantic entity to describe the target image using the one or more semantic entities associated with the at least one similar image; and using, by the one or more processors, the at least one likely semantic entity to provide search results for the target image.