A nominal is an °expression that °can occur on its own and that can serve as an °argument or as an an °adpossessive modifier.
Nominals are often called "nominal phrases" or "NPs" (or "DPs"), but it is not clear how nominals could be defined as kinds of "phrases" (because "phrase" is an abstract notion that is hardly suitable as a comparative concept). Even though "NP" was long the standard term in generative syntax, "nominal" has recently been used increasingly as neutral between "NP" and "DP" (e.g. Bruening 2020).
Nominals could also be defined as "object-denoting referring phrases", as in Croft (2022).
Nominals include independent personal pronouns. If one wants to refer to nominals which are not pronouns, one can use the term "full nominal".
nominal phrase (CXN) = a referring phrase whose head denotes an object concept. Example: a large balloon is a nominal phrase; the head balloon denotes an object concept. A nominal phrase is the prototypical referring phrase, and its head is a noun. (Section 2.2.3)
"Generally speaking languages use either pronouns (such as you and she) or lexical NPs (like the man, two cars, those big trees) to refer to entities. In this book I will mainly restrict myself to lexical NPs which are headed by an underived noun and which are used to refer to a single, discrete, first order (i.e. spatial) entity or to a single individual." (Rijkhoff 2002: §1.5.4)
"I will assume a rather rough characterization of noun phrases, as syntactic constituents which serve as arguments of verbs. There are a variety of ways in which this is inadequate as a precise definition and there are a number of legitimate questions bout exactly what ought to be considered a noun phrase, but these issues are somewhat marginal to the primary purpose of this chapter, which is to discuss some of the ways in which noun phrases differ across languages..." (Dryer 2007: 151)