Dictionary.net

• the connections that link the various parts of an event or argument together; "I couldn't follow his train of thought"; "he lost the thread of his argument"

2006 - WordNet 3.0
By Princeton University

• the connections that link the various parts of an event or argument together; "I couldn't follow his train of thought"; "he lost the thread of his argument"

2011 - English Dictionary Database
By DataStellar Co., Ltd