Pleonasm is the use of more words than are strictly needed to say something. In poetry, it can be a flaw when extra wording only fills out a line, but it can also be a deliberate choice for emphasis, rhythm, or a spoken, expansive voice.
It is not the same as rich description: pleonasm repeats or pads meaning rather than adding clear new detail.
Example
I saw it with my own eyes in the bright noon sun
and heard the silent hush of the empty room.