Should simple but important questions about terminology belong to CSTheory.stackexchange.com?
Questions like this one:
If not, to which site it may be moved?
There are no definitions in Wikipedia's article on programming language.
"A programming language is an artificial language" (1) "designed to express computations that can be performed by a machine, particularly a computer." (2) "Programming languages can be used to create programs that control the behavior of a machine, to express algorithms precisely, or as a mode of human communication." (3)
Intended design purposes cannot be part of definition. So we must omit (2). Usage patterns also cannot be part of definition. So we omit (3). The rest is (1) which is very badly stated and clearly incomplete.
"A programming language is a notation for writing programs, which are specifications of a computation or algorithm."
No definition of program in Wikipedia and one can not define notion referring to other undefined notion.
"A computer program (also a software program, or just a program)" (0) "is a sequence" (1) "of instructions"(2) "written to perform a specified task for a computer." (3)
(1) Programs are clearly not always sequences. For example constraints or expressions are clearly not constitute sequences, but sets and trees correspondingly. (2) Programs are not have to be instructions. Are lambda expressions instructions? (3) intended purpose is not part of definition.
So we have no definition of programming language nor a program in Wikipedia.