How is 'compound noun' defined in CGEL?

Solution 1:

1. Does CGEL define the term word as a lexical unit having no space within when written or printed?

   No, that is not a complete definition of the term "word" as used in the CGEL. The CGEL evidently makes a distinction between the concept of an "orthographic word" and some other concept(s) of "word", as shown in your final quotation, and also in other places. From the chapter "Nouns and noun phrases":

   Like the universal personal pronouns, the reciprocals are written as two orthographic words but are single grammatical words.

   One aspect of the CGEL definition of word that bears noting (since it contradicts the definition used by Greg Lee) is that words apparently cannot contain other words in the CGEL terminological system (based on your third quote). I think this is because "words" in the CGEL are conceived as being the smallest units of syntactic constructions.

2. Does CGEL define the term noun as a single word?

   I'm not certain. Your third quote says that in the compound noun shortbread, bread is a "base" but not a "word", and specifies that it is a base of the type "noun". Since the term "noun" apparently can be applied to the base bread, which is not a word, it seems that being a word in all situations is not a necessary part of the definition of the term "noun". Perhaps "noun" is defined as a construct that can stand as a single word, if not contained in a larger word.

3. (3) Since CGEL says full stop is a compound noun, does the term compound noun as defined in CGEL include not only a single-word unit but also a multiple-word unit?

   I don't know. It would seem inconsistent to me to refer to "full stop" as a word, but not "New Zealand". I'm not sure why "New Zealand" is described as being more than a single word, as I think it is an atomic unit for the purposes of syntax. As far as I can tell, it doesn't pass any of the syntactic tests given in 14.4 for a composite nominal: we can't modify "New" or "Zealand" or coordinate them with other words ("New Zealand and New York" is not replaceable with "New York and Zealand" or "New Zealand and York"). So "New Zealand" seems to me like it should be categorized as a single word, a compound noun.

4. If answers to the above questions are all 'yes', how can you say the term noun is a single-word unit and at the same time that the term compound noun can be a multiple-word unit?

   This looks like a rhetorical question addressed at the authors of the CGEL.

Your first quotation seems entirely irrelevant. That part of CGEL isn't concerned with defining the edges of words; it's about establishing the CGEL's distinction in terminology between "word" and "lexeme," and establishing that different inflected forms of a single lexeme are in the CGEL's terminology called different words.