Non-argument

Non-argument is an NP in A-position, which is not a referential expression and is not assigned a theta-role.

Example
existential there in (i) and expletive it in (ii) are non-arguments.

(i) There is a man in the garden (ii) It is certain that John will win

Idiom chunks such as too much in too much has been made of this problem are also considered non-arguments.

Links
Utrecht Lexicon of Linguistics