In the Legal Theory Lexicon, here.
I've blogged here about why I think "the plain meaning of the text" is incoherent from a perspective informed by knowledge of language and linguistics. Solum's explanation gets around the incoherence by explaining that the "plain meaning of the text" is usually understood not literally as the plain meaning of the text, but rather as "the meaning that would be understood by regular folks who knew that they were reading a statute (or court decision, etc.)."
I think textualists often, but do not always, understand "the plain meaning of the text" this way or similarly, either in terms of "regular folks" or the reasonable reader. That's a topic for another post. For now I will just note the following problem: a reasonable reader or regular person would likely, in a case that is hard to decide for any reason, conclude that the meaning is not straightforward, and that something more is needed to interpret the statute, whether it's evidence of the drafter's intent or a canon of interpretation. And this undermines the purpose of textualism, which is to reduce or eliminate reliance on such sources of evidence.