1. If someone does something at length, they do it after a long period of time. At length my father went into the house. Synonyms: at last, finally, eventually, in time 2. If someone does something at length, they do it for a long time or in great detail. She told us at length about her accident. She was chatting at length about her previous night’s drama with a friend. They spoke at length, reviewing the entire incident. Talk at length = Chat at length = Speak at length Synonyms: for a long time, completely, fully, thoroughly