Commonplace, a.
Common; ordinary; trite; as, a commonplace person, or observation.
3 other Webster entries under this spelling
Commonplace, n.
1. An idea or expression wanting originality or interest; a trite or customary remark; a platitude.
2. A memorandum; something to be frequently consulted or referred to. Whatever, in my reading, occurs concerning this our fellow creature, I do never fail to set it down by way of commonplace. Swift. Commonplace book, a book in which records are made of things to be remembered.
Commonplace, v. t.
To enter in a commonplace book, or to reduce to general heads. Felton.
Commonplace, v. i.
To utter commonplaces; to indulge in platitudes. [Obs.] Bacon.
Shades of meaning
Fernald has no entry of its own for commonplace; he lists it under general.
He lists it without comment; the entries above explain its neighbors.