Title: The Cambridge Dictionary of Philosophy
Content:  The Cambridge Dictionary of Philosophy (1995; second edition 1999; third edition 2015) is a dictionary of philosophy published by Cambridge University Press and edited by the philosopher Robert Audi. There are 28 members on the Board of Editorial Advisors and 440 contributors.
Title: Collins COBUILD Advanced Dictionary
Content:  The Collins COBUILD Advanced Dictionary (CCAD) from HarperCollins, first published in 1987, is a dictionary that distinguished itself by providing definitions in full sentences, rather than excerpted phrases. Example sentences are given for almost every meaning of every word, drawn from a large corpus of actual usage. Except for the 6th edition, it included phonetic transcriptions based on the International Phonetic Alphabet (IPA). In some editions, a digital version on CD-ROM was included with the dictionary in book form. The CCAD seems to be lacking in American English definitions. However, it has an American English equivalent titled Collins COBUILD Advanced Dictionary of American English.
Title: Metalanguage
Content: Audi, R. 1996. The Cambridge Dictionary of Philosophy. Cambridge: Cambridge University Press. ; Baldick, C. 1996. Oxford Concise Dictionary of Literary Terms. Oxford: Oxford University Press. ; Cuddon, J. A. 1999. The Penguin Dictionary of Literary Terms and Literary Theory. London: Penguin Books. ; Honderich, T. 1995. The Oxford Companion to Philosophy. Oxford: Oxford University Press. ; Matthews, P. H. 1997. The Concise Oxford Dictionary of Linguistics. Oxford: Oxford University Press. ISBN: 978-0-19-280008-4. ; McArthur, T. 1996. The Concise Oxford Companion to the English Language. Oxford: Oxford University Press. 
Title: Wolfgang Victor Ruttkowski
Content: Wilfried Kürschner: Linguisten Handbuch, Contemporary Authors, Band 15, Dictionnaire international des termes littéraires, sous la dir. de Jean-Marie Grassin et Joseph Fahey, Wiley Online Library, AbeBooks, ; Marquis: Who`s Who in the World; Nihon Shinshiroku: Who`s Who in Japan 
Title: Webster's Dictionary
Content: Landau, Sidney I. (1989)  Dictionaries:  The Art and Craft of Lexicography.  Cambridge University Press.  Second Edition, 2001. Landau, Sidney I. (1989)  Dictionaries:  The Art and Craft of Lexicography.  Cambridge University Press.  Second Edition, 2001. 
Title: Eugen Wüster
Content: Introduction to the General Theory of Terminology and Terminological Lexicography. Springer, Wien 1979 ; Introduction à la théorie générale de la terminologie et à la lexicographie terminologique. Girsterm, Université Laval, Quebec 1979 ; Introducción a la teoría general de la terminología y a la lexicografía terminológica. Institut Universitari de Lingüística Aplicada (IULA), Universität Pompeu Fabra, Barcelona 1998, ISBN: 84-477-0648-6 (2nd edition 2003) 
Title: Chambers Dictionary
Content:  The Chambers Dictionary (TCD) was first published by William and Robert Chambers as Chambers's English Dictionary in 1872. It was an expanded version of Chambers's Etymological Dictionary of 1867, compiled by James Donald. A second edition came out in 1898, and was followed in 1901 by a new compact edition called Chambers's Twentieth Century Dictionary. TCD is widely used by British crossword solvers and setters, and by Scrabble players (though it is no longer the official Scrabble dictionary). It contains many more dialectal, archaic, unconventional and eccentric words than its rivals, and is noted for its occasional wryly humorous definitions. Examples of such definitions include those for éclair ("a cake, long in shape but short in duration") and middle-aged ("between youth and old age, variously 
Title: Charles Stevenson (philosopher)
Content: The Penguin Dictionary of Philosophy, ed. Thomas Mautner. Penguin Putnam Inc. ISBN: 0-14-051250-0 The Penguin Dictionary of Philosophy, ed. Thomas Mautner. Penguin Putnam Inc. ISBN: 0-14-051250-0 
Title: Philosophy
Content:  ; Mautner, T., Ed. The Penguin Dictionary of Philosophy. London, Penguin Books. ; Runes, D., Ed. (1942). The Dictionary of Philosophy . New York, The Philosophical Library, Inc. ; Angeles, P.A., Ed. (1992). The Harper Collins Dictionary of Philosophy. New York, Harper Perennial. ; Hoffman, Eric, Ed. (1997) Guidebook for Publishing Philosophy. Charlottesville, Philosophy Documentation Center. ; Popkin, R.H. (1999). The Columbia History of Western Philosophy. New York, Columbia University Press. ; Bullock, Alan, and Oliver Stallybrass, jt. eds. The Harper Dictionary of Modern Thought. New York: Harper & Row, 1977. xix, 684 p. N.B.: "First published in England under the title, The Fontana 
Title: Wolfgang Victor Ruttkowski
Content:  Sangyo University (1983–2003), he made contact with many internationally known colleagues. With six colleagues he published a 7-language (German-English-French-Italian-Spanish-Dutch-Russian) literary dictionary (Nomenclator Literarius, Francke, 1980). It contains 2,604 groups of terms and an extensive index, with the Russian terms also in Cyrillic script. It sold out almost immediately, mainly to libraries and comparatists. All of these books (and several others, in total 44 books and booklets) were re-published by Igel Verlag (Hamburg) and Grin Verlag (Munich). Thus, Ruttkowski is most likely the most published author in the fields of Poetics of Literary Genres, Psychology of Literature and Literary Terminology.

Question: Who is the author of Definitions?
Answer: Speusippus.