The “input validation” term is extremely common, but it is used in many different ways. In some cases its usage can obscure the real underlying weakness or otherwise hide chaining and composite relationships.
Some people use “input validation” as a general term that covers many different neutralization techniques for ensuring that input is appropriate, such as filtering, canonicalization, and escaping. Others use the term in a more narrow context to simply mean “checking if an input conforms to expectations without changing it.” CWE uses this more narrow interpretation.