In traditional English lexicography, individual dictionary editors have had ultimate control over the selection, meaning, and illustration of words and extensive collaboration with contributors has been limited. However, Internet technologies that easily permit exchanges between a user and a database have allowed a new type of dictionary online: one that is built by the collaboration of contributing end-users, allowing users who are not trained lexicographers to engage in the actual making of dictionaries. We discuss here a popular online slang dictionary, UrbanDictionary.com (UD), to illustrate how traditional lexicographic principles are joined with Web-only communication technologies to provide a context for collaborative engagement and meaning-making, and to note the many characteristics and functions shared with traditional print dictionaries. Significantly, UD captures what most traditional English dictionaries fall short of: both recording ephemeral everyday spoken language and representing popular views of meaning. By relying on the users of language to select and define words for a dictionary, UD – which defines more than one million words – has in effect influenced both access to and formulation of the lexis.