Johnsonian describes writing that imitates Samuel Johnson's elevated, forceful style: formal diction, balanced syntax, moral seriousness, and a slightly heavy, rhetorical quality. In poetry, the word usually points to a poem or line that sounds learned, polished, and deliberate rather than light or conversational.
The term is most often used of style, not subject matter, and it can suggest admiration or criticism depending on context.
Example
The old clock spoke with a Johnsonian air:
Its measured voice condemned each wasted hour,
And every tick seemed clothed in sober power.